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1.   DER    Radon Mitigation Standards  RMS      detailed and final Pennsylvania Radon Mitigation Standards  PA RMS  set forth in this  document     2 0 PURPOSE    The purpose of the PA RMS is to provide radon mitigation contractors with uniform standards  that will ensure quality and effectiveness in the design  installation  and evaluation of radon  mitigation systems in detached and attached residential buildings three stories or less in height   The PA RMS is intended to serve as a model set of requirements which have been adopted by  the Pennsylvania Department of Environmental Protection  PA DEP  to fulfill the requirements  of the Radon Certification Act  25 Pa  Code  Chapter 240     3 0 PARTICIPANTS    The minimum requirements for individuals or firms who perform radon remediation work within  the Commonwealth  include  completion of Radon Certification Application  Radon Mitigation    attend a Department approved course  have one year radon mitigation experience or three years  experience in architecture  engineering  electrical  plumbing carpentry  masonry  or related  trades  pass the EPA Radon Contractors Proficiency exam  and submit the required fee     4 0 SCOPE    The requirements addressed in the PA RMS include the following categories of contractor  activity  general practices  building investigation  worker health and safety  systems design   systems installation  materials  monitors and labeling  post mitigation testing  and contacts and  documentation     5 0
2.   statement that the system is temporary and that it will be replaced with a permanent system  within 30 days  The label shall also include the date of installation  and the contractor s name   phone number  and PA DEP certification Identification Number   EXCEPTION  The 30 day    9 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      limit on use of a temporary mitigation system may be extended in cases where a major  renovation or change in building use necessitates a delay in installation of a permanent  mitigation system that is optimized to the new building configuration or use  DEP   s Bureau of  Radiation Protection should be notified in writing when this exception is being applied      10 4 When the selected mitigation technique requires use of sealants or caulks containing  volatile solvents  prior to starting work  the contractor shall inform the client in writing  this  could include an MSDS sheet  of the need to ventilate work areas during and after the use of  such sealants  Ventilation shall be provided as recommended by the manufacturer of the  material     11 0 BUILDING INVESTIGATION    11 1 The contractor shall conduct a thorough visual inspection of the building prior to  initiating any radon mitigation work  This inspection should be performed prior to submission of  the bid proposal to the client  The inspection is intended to identify any specific building  characteristics or configurations  e g   large 
3.  4 Where installation of a radon mitigation system requires pipe or ducts to penetrate a  firewall or other fire resistance rated wall or floor  penetrations shall be protected in accordance  with applicable building  mechanical  fire  and electrical codes     14 1 5 When installing radon mitigation systems that use sump pits as the suction point for  active soil depressurization  if sump pumps are needed  it is recommended that submersible  sump pumps be used   See paragraphs 14 5 1  14 7 4  15 7  and 15 8      14 2 Radon Vent Pipe Installation Requirements    14 2 1 All joints and connections in radon mitigation system vent pipes shall be permanently  sealed as specified by the manufacturer  with the exception that flexible rubber couplings are an  allowable altemative method     14 2 2 Radon vent pipe runs subjected to cold environments should be insulated to prevent  vent pipe freeze up  Radon vent pipes in attics where warm  moist environments exist should  also be insulated to reduce condensation on exterior pipe surfaces     14 2 3 Radon vent pipes shall be fastened to the structure of the building with hangers   strapping  or other supports that will adequately secure the vent material  Existing plumbing  pipes  ducts  or mechanical equipment shall not be used to support or secure a radon vent pipe     14 2 4 Supports for radon vent pipes shall be installed at least every 6 feet on horizontal runs  to eliminate vertical or horizontal movement  Vertical runs shall be s
4.  ASSUMPTION   Before applying the provisions of the PA RMS  it is assumed that appropriate radon radon decay  product measurements have been performed within the structure  and that the owner has decided  that radon remediation is necessary     6 0 IMPLEMENTATION   6 1 The PA RMS includes requirements for installation of radon remediation systems and  provides a basis for evaluating the quality of those installations  All PA DEP certified  contractors are required to follow all requirements set forth in the PA RMS    6 2 Contractors shall personally conduct follow up inspection of any radon mitigation system  installed by their firm that was changed from the original certified contractors design     2 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      Additionally  contractors shall inspect 20 percent of all other installations  within 30 days of  system completion to insure continued conformance to PA RMS     6 3 PA DEP will inspect radon mitigation systems installed by DEP  certified contractors for  compliance with this standard and the PA DEP Radon Certification Regulations  25 Pa  Code  Ch  240   Violations of these standards and regulations may result in decertification  suspension  of certification  or civil penalties  Additionally  state radon program personnel are considered  agents of the US EPA  and as such any inspection finding may be forwarded to the US EPA for  evaluation of noncompliance with these standard
5.  Houses  Technical Guidance  Third  Edition  for Active Soil Depressurization Systems  EPA 625 R  93 011  October 1993     4 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS    8 5  Application of Radon Reduction Methods   EPA 625 5  88 024  August 1988     8 6  Indoor Radon and Radon Decay Product Measurement Device Protocols   EPA  402 R 92 004  July  1992     8 7  Protocols for Radon and Radon Decay Product Measurements in Homes   EPA  402 R 92 003  June  1993    8 8  A Citizen s Guide to Radon  Second Edition   EPA 402 K92 001  May 1992     8 9  Pennsylvania s Consumers Guide to Radon Reduction   EPA  402 K92 003  August   1992     8 10    Pennsylvania s Home Buyer s and Sellers Guide to Radon   EPA 402 R 93 003  March   1993     8 11  ASHRAE Standard 62 1989   Appendix B  Positive Combustion Air Supply     8 12  National Gas Code   Appendix H  p 2223  1 98   1988  Recommended Procedure for  Safety Inspection of an Existing Appliance Installation     8 13   Chimney Safety Tests User s Manual   Second Edition  January 12  1988  Scanada  Shelter Consortium Inc   for Canada Mortgage and Housing Corp     8 14    The Spillage Test    Method to Determine the Potential for Pressure  Induced Spillage  from Vented  Fuel Fired  Space Heating Appliances  Water Heaters and Fireplaces  Canadian  General Standards Board  CAN CGSB  51 71 95  April 1995     8 15 OSHA  Safety and Health Regulations for Construction  Ionizing Radiation   2
6.  a subslab depressurization system is contemplated and characteristics of  the subslab material are unknown  a communication test  as defined in paragraph 9 9 is  recommended     11 5 As part of the building investigation  a floor plan sketch shall be developed  if not already  in existence and readily available  that includes illustrations of the building foundation   slab on grade  basement or crawlspace area   The sketch should include the location of load  bearing walls  drains  sump pits  HVAC systems and natural draft appliances  It shall be  annotated to include the anticipated layout of any radon mitigation system piping  and the  anticipated locations of any vent fan and system waming devices for the envisioned mitigation  systems  The sketch shall be finalized during installation and shall be included in the  homeowner information package   paragraph 18 5      12 0 WORKER HEALTH AND SAFETY  12 1 The contractor shall comply with all OSHA  state and local standards or regulations  relating to worker safety and occupational radon exposure  Applicable references in the Code of    Federal Regulations and NIOSH publications  or subsequent updates  are listed in paragraphs  8 15  8 16  and 8 17     11 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      12 2 In addition to the OSHA and NIOSH standards  the following requirements that are  specifically or uniquely applicable for the safety and protection of radon mitigatio
7.  as the vent pipes  unless flexible  airtight rubber couplings are used   See paragraph 14 3 7 for exception when  installing vent fans  and paragraph 14 2 7 for exception when installing radon vent pipes in sump  pit covers      15 4 Cleaning solvents and adhesives used to join pipes and fittings shall be as recommended  by manufacturers for use with the type of piping material used in the mitigation system     15 5 When sealing cracks in slabs and other small openings around penetrations of the slab and  foundation walls  caulks  and sealants designed for such application shall be used  Urethane  sealants are recommended because of their durability     15 6 When sealing holes for plumbing rough in or other large openings in slabs and foundation  walls that are below the ground surface  nonshrink mortar  grouts  expanding foam or other  comparable materials for such application shall be used     15 7 Sump pit covers shall be made of durable plastic  galvanized sheet metal  aluminum  or   southem pine treated  CCA  see 9 4  for ground contact  and designed to permit airtight sealing  to the slab surface surrounding the sump pit  To permit easy removal for sump pump servicing    the cover shall be sealed to the slab surface using silicone or other nonpermanent type caulking   materials or an airtight gasket  Sump covers should have a window to observe conditions in the  sump pit     20 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standar
8.  cited in paragraph 8 2  8 4  and 8 19     15 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      14 3 3 Radon vent fans used in active soil depressurization or block wall depressurization  systems shall not be installed below grade nor in the conditioned  heated cooled  space of a  building  nor in any basement  crawlspace  or other interior location directly beneath the  conditioned spaces of a building  Acceptable locations for radon vent fans include attics not  suitable for occupancy  including attics over living spaces and garages   garages that are not  beneath conditioned spaces  or on the exterior of the building     14 3 4 Radon vent fans shall be installed in a configuration that avoids condensation buildup  in the fan housing  Active soil depressurization fans shall be installed in vertical runs of the vent  pipe     14 3 5 Radon vent fans mounted on the exterior of buildings shall be rated for outdoor use or  installed in a water tight protective housing     14 3 6 Radon vent fans shall be mounted and secured in a manner that minimizes transfer of  vibration to the structural framing of the building     14 3 7 To facilitate maintenance and future replacement  radon vent fans shall be installed in  the vent pipe using removable  air tight couplings or flexible connections that can be tightly  secured to both the fan and the vent pipe     14 3 8 The intakes of fans used in crawlspace pressurization  or in pressur
9.  of the contractor to seal shall be disclosed to  the client and included in the documentation     If it is determined between contractor and homeowner that the perimeter channel drain  can not be sealed for water control reasons  the contractor may leave this perimeter channel drain  unsealed  However  the contractor shall provide in writing to the homeowner the following    1 this technique may contribute to an increased heating and cooling penality   2 the efficiency  of the radon mitigation system may be decreased   3 there may be a increase in the potential for  backdrafting natural draft combustion appliances  and  4 radon levels should still be reduced to  less than 4 0 pCi l     14 5 5 When installing baseboard type suction systems  all seams and joints in the baseboard  material shall be joined and sealed using materials recommended by the manufacturer of the  baseboard system  Baseboards shall be secured to walls and floors with adhesives designed and  recommended for such installations  If a baseboard system is installed on a block wall  foundation  the tops of the blockwall shall be closed and sealed as prescribed in paragraph  14 5 3     14 5 6 Any seams in soil gas retarder membranes used in crawlspaces for sub membrane  depressurization systems shall be overlapped at least 12 inches and should be sealed  To    17 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      enhance the effectiveness of submembrane depr
10.  steps designed to reduce radon concentrations in the  indoor air of a building     9 15 Mechanically Ventilated Crawlspace System  A radon control technique designed to  increase ventilation within a crawlspace  achieve higher air pressure in the crawlspace relative to  air pressure in the soil beneath the crawlspace  or achieve lower air pressure in the crawlspace  relative to air pressure in the living spaces  by use of a fan   See also paragraph 9 11  Crawlspace  Depressurization      9 16 Natural Draft Appliance  Any combustion appliance that does not have fan forced  combustion venting and therefore is more likely to be susceptible to backdrafting     9 17 pCi l  The abbreviation for picocuries per liter which is a unit of measure for the amount    of radioactivity in a liter of air  There are 2 2 disintegrations per minute of radioactive  material in 1 picocurie     7 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      9 18 Perimeter Channel Drain  A means for collecting water in a basement by means of a  large gap or channel between the concrete floor and the wall  Collected water may flow to  aggregate beneath the channel   French Drain    or to a sump where it can be drained or pumped  away     9 19 Pressure Field Extension  The distance that a pressure change is induced in the subslab  area  measured from a single or multiple suction points   See also paragraph 9 9   Communication Test      9 20 Radon  A naturall
11.  to retest the building at least every two years  Retesting is also  recommended if the building undergoes significant alteration     17 6 The contractor shall continue to abide by the reporting requirements  Section 240 303  of  the Radon Certification Regulations     18 0 CONTRACTS AND DOCUMENTATION  18 1 The following information shall be provided to the clients prior to initiation of work    1  The contractors PA DEP identification number      2  A statement that describes the planned scope of work     22 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS       3  A statement describing any known hazards associated with chemicals used in or as part of  the installation      4  A statement indicating compliance with and implementation of all PA DEP standards and  those of other agencies having jurisdiction  e g  code requirements       5  A statement describing any system maintenance that the building owner would be required  to perform      6  The installation cost  and an estimate of the annual operating costs of the system     7  The terms of any warranty or guarantee     8  Notice to Clients   18 2 Contractors shall keep records of all radon mitigation work performed and maintain those  records for two years or for the period of any warranty or guarantee  whichever is longer  These  records shall include the information as outlined in the Radon Certification Regulations  Section  240 303  Additional records that should b
12. 9 CFR  1926 53     8 16 OSHA  Occupational Safety and Health Regulations  Ionizing Radiation   29 CFR  1910 96     8 17 NIOSH  Guide to Industrial Respiratory Protection   DHHS  NIOSH  Publication NO   87 116  September 1987     8 18 NCRP  Measurement of Radon and Radon Decay Daughters in Air   NCRP Report No   97  Nov 1988     5 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      8 19 EPA  Handbook  Sub Slab Depressurization for Low Pemmeability Fill Material    EPA 625 6  91 029  July 1991     9 0 DESCRIPTION OF TERMS    For this document  certain terms are defined in this section  Terms not defined herein should  have their ordinary meaning within the context of their use  Ordinary meaning is as defined in   Webster s Ninth New Collegiate Dictionary      9 1 Backdrafting  A condition where the normal movement of combustion products up a flue   resulting from the buoyant forces on the hot gases  is reversed  so that the combustion products  can enter the structure  Backdrafting of combustion appliances  such as fireplaces and fumaces   can occur when depressurization in the structure overwhelms the buoyant force on the hot gases   Backdrafting can also be caused by chimney blockage     9 2 Backer Rod  A semirigid closed cell foam material resembling a rope of various  diameters  Used to fill around pipes  large cracks etc  to assist in making a sealed penetration   For example  where a pipe is inserted through a concrete 
13. Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      CONTENTS  1 0  Backgro    d   issia andi anan tees aatn amc Na taaa baee EEan 1  20  PUNPOSC i  isana E a ea aE a EENE aSa Tani eaaa 2  3 0  ParbepaniS aaa enemiet aara nEaN ACUAN APANE NEEE DiN 2  4 0  SCOPE  s aaa araa nea aaee Eea Aaa enaa Oain ae Tena EIEE 2  5 0  ASS  MPI  N  J teicnasicccccapsrccceanasnsassanecnscaceeensacniausacavedsaenensnaate 2  6 0 Implementatio Rise bsse fidence lanasacuen tidt eased dnckenilsivendaxencdenebens 3  TO   MATION ii os cca das E E AEE vie EEEE E 3  8 0 Reference DOCUMENMS               c ceceeceeeceenecereceeeeeeeeseeenereres 5  9 0 Description of Tennis sicicececsaisnwinnecnaasiisdadeieennssadanaciansevniene 7  10 0      General Practices vcs sesceivasscinc ceo occ astaasepee aseessa kiant 9  11 0 Building Investigation               c ccceceseeeeeeeeeeeeeeeeeeeeeeeeeneneneees 10  12 0 Worker Health and Safety        0    ccceseeseeeeeeeeeeeeeeeeeeeeeeeeeense 11  13 0 Systems Design            c ceeceeeeeeeeeeeeceeceeeeceeceeeseeseeeeeeeeeeeeees 13  14 0 Systems Installations              ccceceeeee eee ee eee eee eee e eee eee eee eeneeee 14   1 General Requirement               ceceeeeceeeeeeeeeeeeeeeeeeees 14  Radon Vent Pipe Installation Requirements                 14  3 Radon Vent Fan Installation Requirements                  15   4 Suction Pit Requirements for SSD Systems                 16   5 Sealing Requirements              ceec
14. ble Exposure Limits  the contractor shall ensure that employee s are exposed to no more  than 4 working level months  WLM  over a 12 month period   An equilibrium ratio of 50  percent shall be used to convert radon exposure to WLM   If a contractor is a sole proprietor of  a radon mitigation firm they are still responsible for recording and maintaining their own  occupational radon radon progeny exposure     12 2 9 In any area where building materials containing friable asbestos have been identified   or it is suspected that friable asbestos may exist  radon mitigation work shall not be conducted  without the approval of an inspector or mitigator certified under provisions of the Asbestos  Hazards Emergency Response Act  AHERA  and the Pennsylvania Department of Labor and  Industry Act 194     12 2 10 When mitigation work requires the use of sealants  adhesives  paints  or other  substances that may be hazardous to health  the contractor shall provide employee s with the  applicable Material Safety Data Sheets  MSDS  and explain the required safety procedures     13 0 SYSTEMS DESIGN    13 1 All radon mitigation systems shall be designed and installed as permanent  integral  additions to the building  except where a temporary system has been installed in accordance with  paragraph 10 3  The radon mitigation system shall exist as a stand alone system and not  incorporate other house systems or features in its design     13 2 All radon mitigation systems shall be designed to avo
15. cracks in slabs  exposed earth in crawlspaces  open  sump pits  wet basement or foundation walls  that may affect the design  installation  and  effectiveness of radon mitigation systems  As a part of this inspection  clients should be asked to  provide any available information about the building  e g   construction specifications  pictures   drawings  etc   that might be of value in determining the radon mitigation strategy     11 2 To facilitate selection of the most effective radon control system and avoid the cost of  installing systems that subsequently prove to be ineffective  it is recommended that the  contractor conduct diagnostic tests to assist in identifying and verifying suspected radon sources   entry points  and subslab communication  Radon grab sampling  communication tests  and use  of chemical smoke sticks are examples of the type of diagnostic testing commonly used   See  paragraph 11 4      11 3 It is recommended that during the building investigation  the contractor routinely perform  diagnostic tests to evaluate the existence of  or the potential for  backdrafting of natural draft  combustion appliances  Published procedures for conducting backdrafting tests are covered in  the Reference Documents listed in paragraphs 8 11  8 12 8 13 and 8 14  The following checklist  has been extracted from material in these references and may be used to test for existing or  potential backdrafting conditions      1  Close all extemal windows and doors and the door bet
16. ds  RMS      15 8 Penetrations of sump covers to accommodate electrical wiring  water ejection pipes  or  radon vent pipes shall be designed to pennit airtight sealing around penetrations  using caulk or  grommets     15 9 Plastic sheeting installed in crawlspace as soil gas retarders shall be a minimum of 6 mil   3 mil cross laminated  polyethylene or equivalent flexible material  Heavier gauge sheeting  should be used when crawlspaces are used for storage  or frequent entry is required for  maintenance of utilities     15 10 Any wood in contact with soil or soil gas  used to attach soil gas retarder membranes to  crawlspace walls or piers shall be pressure treated or naturally resistant to decay and termites     16 0 MONITORS AND LABELING    16 1 All active radon mitigation systems shall include a mechanism to monitor system  performance by use of a magnehelic gauge  manometer or a comparable mechanism  The  mechanism shall be simple to read or interpret and be located where it is easily seen by building  occupants and in an area where it would be unlikely to be damaged  The final system vacuum  shall be indicated on the gauge for future reference as measured at the gauge location     16 2 Electrical radon mitigation system monitors  whether visual or audible  shall be installed  on nonswitched circuits and be designed to reset automatically when power is restored after  service or power supply failure  Audible alarms shall include a disconnect mechanism separate  from the 
17. e  National Electric Code and any additional local regulations     14 6 2 Wiring shall not be located in or chased through the mitigation installation ducting or  any other heating or cooling ductwork     14 6 3 Any plugged cord used to supply power to a radon vent fan shall be no more than 6  feet in length     14 6 4 No plugged cord shall penetrate a wall or be concealed within a wall     14 6 5 Radon mitigation fans installed on the exterior of buildings shall be hard wired into an  electrical circuit unless a UL approved continuous duty exterior plug method is used     14 6 6 If the rated electrical requirements of a radon mitigation system fan exceeds 50  percent of the circuit capacity into which it will be connected  or if the total connected load on  the circuit  including the radon vent fan  exceeds 80 percent of the circuit s rated capacity  a  separate  dedicated circuit shall be installed to power the fan     18 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      14 6 7 An electrical disconnect switch or circuit breaker shall be installed in radon mitigation  system fan circuits to permit deactivation of the fan for maintenance or repair by the building  owner or servicing contractor   Disconnect switches are not required with plugged fans      14 7 Drain Installation Requirements    14 7 1 If drains discharge directly into the soil beneath the slab or through solid pipe to a  soak away  the contractor shall ins
18. e by snow or leaves and be a minimum of 10 feet apart     14 8 5 Contractors installing HRV systems shall verify that the incoming and outgoing  airflow is balanced to ensure that the system does not create a negative pressure within the  building  Contractors shall inform building owners that periodic filter replacement and inlet grill  cleaning are necessary to maintain a balanced airflow  This information shall also be included in  the documentation  An inclined manometer should be installed across the intake filter to  indicate the need for filter cleaning or replacement     19 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      14 8 6 Both intemal and extemal intake and exhaust vents in HRV systems shall be covered  with wire mesh or screening  typically 1 4 by 1 4   to prevent entry of animals or debris or injury  to occupants     15 0 MATERIALS    15 1 All mitigation system electrical components shall be U L  listed or of equivalent  specifications     15 2 As a minimum  all plastic vent pipes in mitigation systems shall be made of Schedule 20  PVC  ABS or equivalent piping material  Schedule 40 piping or its equivalent should be used in  garages and in other intemal and extemal locations subject to physical damage  PVC pipe  exposed to sun light should be formulated for outdoor use and painted to provide protection  against UV radiation     15 3 Vent pipe fittings in a mitigation system shall be of the same material
19. e kept include     1  The Building Investigation Summary and floor plan sketch   See Appendix A      2  Pre and post mitigation radon test data     3  Pre and post mitigation diagnostic test data     4  Copies of contracts and warranties      5  A narrative or pictorial description of mitigation system s  installed     18 2 1 Appendix A contains a suggested standard format for compiling mitigation project  records     18 3 Other records or bookkeeping required by the PA DEP  25 Pa  Code Ch  240   local  and  Federal statutes and regulations shall be maintained for the periods prescribed by those    requirements     18 4 Health and safety records  including worker radon exposure logs  shall be maintained  indefinitely     23 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      18 5 Upon completion of the mitigation project  the contractor shall provide clients with an  information package that shall include  but is not limited to      1  A completed copy of the PA DEP Bureau of Radiation Protection  Radon Division    Radon Mitigation Project Record   Appendix A      2  A final system layout that has its components labeled on a floor plan     3  Copies of contracts and warranties     4  A description of the installed mitigation system  its basic operating principles     5  A description of any deviations from the RMS or State requirements     6  A description of the proper operating procedures of any installed mechanical or el
20. ectrical  systems  including manufacturer s operation and maintenance instructions  drain filling    instructions  and how to interpret waming devices      7  A list of appropriate actions for the client to take if the system failure warming device  indicates system degradation or failure      8  A recommendatio n to retest at least every two years      9  A recommendation to have an electrical inspection performed on the applicable  components of the installed system      10  This information package shall be attached to the mitigation system in a secure and  permanent manner  in a visible location  and Labeled   Radon Mitigation Information      DISCLAIMER    The Pennsylvania Department of Environmental Protection  PA DEP  strives to  provide accurate  complete  and useful information  However  neither PA DEP nor any  person contributing to the preparation of this document makes any warranty  express or  implied  with respect to the usefulness or effectiveness of any information  method  or  process disclosed in this material  DEP does not assume any liability for the use of  or  damages arising from the use of  any information  method  or process disclosed in this  document  Mention of firms  trade names  or commericial products does not  constitute endorsement or recommendation for use     24 of 24    
21. ecured either above or  below the points of penetration through floors  ceilings  and roofs  or at least every 8 feet on runs  that do not penetrate floors  ceilings  or roofs     14 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      14 2 5 To prevent blockage of air flow into the bottom of radon vent pipes  these pipes shall  be supported or secured in a permanent manner that prevents their downward movement to the  bottom of suction pits or sump pits  or into the soil beneath an aggregate layer under a slab     14 2 6 Radon vent pipes shall be installed in a configuration that ensures that any rain water  or condensation within the pipes drains downward into the ground beneath the slab or soil gas  retarder membrane     14 2 7 Radon vent pipes shall not block access to any areas requiring maintenance or  inspection  unless the vent pipe is designed for easy removal and air tight replacement  Radon  vent pipes shall not be installed in front of or interfere with any light  opening  door  window or  equipment access area required by code  If radon vent pipes are installed in sump pits  with  sump pumps   the system shall be designed with removable  air tight  couplings to facilitate  removal and reinstallation of the vent pipes and sump pit cover for sump pump maintenance     14 2 8 To prevent reentrainment of radon  the point of discharge from vents of fan powered  soil depressurization and block wall depressurization sys
22. ed  i e   postmitigation radon levels shall be less than 4 pCi l  and the  systems design criteria in paragraph 13 0 shall be applied  A contractor who expects to deviate  from proven radon mitigation technologies and methods  as defined in the PA RMS and other  EPA references in Section 8 0  for purposes of research on innovative mitigation techniques  or  for other reasons  shall  prior to initiation of work  obtain approval from PA DER  document the  nonstandard techniques  and inform the client of the deviation from standard procedures     7 7 At this time  the PA RMS does not include standards for installing systems to mitigate  radon in water  However  EPA is currently developing a standard that will regulate radon levels  in domestic water supplies  Following publication of that standard  the PA RMS may be revised   as appropriate  to include standards for installation of systems that are effective in reducing  radon levels in water     8 0 REFERENCE DOCUMENTS    The following documents are sources of additional radon mitigation information and are  recommended reading for contractors participating in the RCP program     8 1 EPA Radon Mitigation Standards  April 1994 Revised Edition  EPA 402 R  93 078   8 2 EPA Training Manual  Reducing Radon In Structures    Third Edition   January 1993     8 3  Radon Reduction Techniques for Detached Houses  Technical Guidance  Second  Edition   EPA 625 5  87 019  January 1988     8 4  Radon Reduction Techniques for Existing Detached
23. eeeeeeeeeeeeeeneeeeeeeenss 16  6 Electrical Requiremenits              cccceeeseeeeeeeeeeeeeenenees 18  7 Drain Installation Requirements                 cscsceseseseeee 19   8 HVAC Installation Requirements               0seecseseeeeee 19  45 0  Mate  alS  iein ae cue hie sek tiae cent boxe Oradea aa aaar ai 20  16 0 Monitors and Labeling              ceceseseeeeeeeeeeeeeeeeeeeeeeeeeeeeeeenenens 21  17 0 Postmitigation TeSting           0 cececeeeeeeeeeeeeeseeeseeeeeeeeseeeneneneeees 22  18 0 Contracts and Documentation          2   0sceceeeeeeeeeeeeeeeeeeeeeeneemees 22  DISCLAIMER       schiec sa ctescav eee baru cused dadaeeateven ata reeel  enue 24    1 0 BACKGROUND    The 1988 Indoor Radon Abatement Act  IRAA  required the Environmental Protection Agency   EPA  to develop a voluntary program to evaluate and provide information on contractors who  offer radon control services to homeowners  The Radon Contractor Proficiency  RCP  Program  was established to fulfill this portion of the IRAA  In December 1991  EPA published  Interim  Radon Mitigation Standards  as initial guidelines for evaluating the performance of radon  mitigation contractors under the RCP Program  Over the past six years  the effectiveness of the  basic radon mitigation techniques set forth in the  Interim Standards   has been validated in field  applications throughout the United States  This experience now serves as the basis for the more    1 of 24    Pennsylvania Department of Environmental Resources
24. essurization systems  the membrane should also  be sealed around interior piers and to all crawlspace wall surfaces  All sealants shall be  long lived  Duct tape is not a long lived sealant     14 5 7 In combination basement crawlspace foundations  where the crawlspace has been  confirmed as a source of radon entry  and membrane depressurization is not a viable mitigation  option  access doors and other openings between the basement and the adjacent crawlspace shall  be closed and sealed  Access doors required by code shall be fitted with air tight gaskets and a  means of positive closure  but shall not be permanently sealed  In cases where both the  basement and the adjacent crawlspace areas are being mitigated with active SSD and SMD  systems  sealing of the openings between those areas is not required     14 5 8 When crawlspace depressurization is used for radon mitigation  openings and cracks  in floors above the crawl space which would pemnit conditioned air to pass out of the living  spaces of the building  should be identified and sealed in a permanent manner  Sealing of  openings around hydronic heat or steam pipe penetrations should be done using noncombustible  materials  Openings and cracks that are determined to be inaccessible or beyond the ability of  the contractor to seal should be disclosed to the client and included in the documentation     14 6 Electrical Requirements    14 6 1 Wiring for all active radon mitigation systems shall conform to provisions of th
25. ication Test  A diagnostic test designed to qualitatively measure the ability of a  suction field and air flow to extend through the material beneath a concrete slab floor and thus  evaluate the potential effectiveness of a subslab depressurization system  This test is commonly  conducted by applying suction to a hole drilled through the slab where a future suction hole  might be located and simultaneously measuring the pressure differential or observing the  movement of smoke downward into small holes drilled in the slab at locations away from the  suction hole   See also paragraph 9 19  Pressure Field Extension      9 10 Contractor  An individual or firm listed with the PA DEP as being certified to perform  radon mitigation activities     9 11 Crawlspace Depressurization  A radon control technique designed to achieve lower air  pressure in the crawlspace relative to indoor air pressure by use of a fan powered vent drawing  air from within the crawlspace   See also paragraph 9 15 Mechanically Ventilated Crawlspace  System      9 12 Diagnostic Tests  Procedures used to identify or characterize conditions within buildings  that may contribute to radon entry or elevated radon levels or may provide information regarding  the performance of a mitigation system     9 13 Drain Tile Loop  A continuous length of drain tile or perforated pipe extending around  all or part of the internal or extemal perimeter of a basement or crawlspace footing     9 14 Mitigation System  Any system or
26. id the creation of other health   safety  or environmental hazards to building occupants  such as backdrafting of natural draft  combustion appliances     13 3 All radon mitigation systems shall be designed to maximize radon reduction  while  minimizing excess energy usage  avoiding compromise of moisture and temperature controls and  other comfort features  and minimizing noise     13 4 All radon mitigation systems and their components shall be designed to comply with the    laws  ordinances  codes  and regulations of relevant jurisdictional authorities  including  applicable mechanical  electrical  building  plumbing  energy  and fire prevention codes     13 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      14 0 SYSTEMS INSTALLATION    14 1 General Requirements    14 1 1 All components of radon mitigation systems installed in compliance with provisions  of the PA RMS shall also be in compliance with the applicable mechanical  electrical  building   plumbing  energy and fire prevention codes  standards  and regulations of the local jurisdiction     14 1 2 The contractor shall obtain all required licenses and permits  and display them in the  work areas as required by local ordinances     14 1 3 Where portions of structural framing material must be removed to accommodate  radon vent pipes  material removed shall be no greater than that permitted for plumbing  installations by applicable building or plumbing codes     14 1
27. in a  permanent  airtight manner using compatible caulks or other sealant materials   See paragraph  15 5  Openings around other utility penetrations of the slab  walls  or soil gas retarder shall also  be sealed     14 5 3 Where a Block Wall Depressurization  BWD  system is used to mitigate radon   openings in the tops of such walls and all accessible openings or cracks in the interior surfaces of  the walls shall be closed and sealed with urethane or equivalent caulks  expandable foams  rigid  board stock caulked in place  nonshrink grout or other comparable materials   See paragraphs  15 5 and 15 6   Openings or cracks that are determined to be inaccessible or beyond the ability  of the contractor to seal shall be disclosed to the client and included in the documentation     14 5 4 Openings  perimeter channel drains  or cracks that exist where the slab meets the  foundation wall  floor wall joint   shall be sealed with urethane caulk or equivalent material   When the opening or channel is greater than 1 2 inch in width  a foam backer rod or other  equivalent filler material shall be inserted in the channel before application of the sealant   Materials inserted into the channel shall leave adequate space below the filler material to allow  sub surface drainage from the channel into the sub slab material  Other openings or cracks in  slabs or at expansion or control joints should also be sealed  Openings or cracks that are  determined to be inaccessible or beyond the ability
28. izing the building  itself  shall be screened or filtered to prevent ingestion of debris or personal injury  Screens or  filters shall be removable to permit cleaning or replacement and building owners shall be  informed of the need to periodically replace or clean such screens and filters  This information  shall also be included in the documentation   See paragraph 18 5      14 4 Suction Pit Requirement for Subslab Depressurization  SSD  Systems    14 4 1 To provide optimum pressure field extension of the subslab communication zone  a  minimum of 1 2 cubic foot  i e  approx  half of a 5 gallon bucket  of material shall be excavated   unless bedrock prohibits this  from the area immediately below the slab penetration point of  SSD system vent pipes     14 5 Sealing Requirements    14 5 1 Sump pits that permit entry of soil gas or that would allow conditioned air to be drawn  into a subslab depressurization system shall be covered and sealed  The sump cover shall have a  radon resistant drain  See paragraph 9 21  if there is no other available floor drain   Homeowner  information should indicate periodic filling  if applicable   See paragraph 15 7 for details on  sump cover and sealing materials     16 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      14 5 2 Openings around radon vent pipe penetrations of the slab  the foundation walls  and  the crawlspace soil gas retarder membrane shall be cleaned  prepared  and sealed 
29. ling of these membranes is recommended     9 28 Subslab Depressurization  Active   A radon control technique designed to achieve    lower subslab air pressure relative to indoor air pressure by use of a fan powered vent drawing  air from beneath the concrete slab     8 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      9 29 Subslab Depressuri zation  Passive   A radon control technique designed to achieve  lower subslab air pressure relative to indoor air pressure by use of a vent pipe  without a fan   routed through the conditioned space of a building and connecting the subslab area to the  outdoor air  This system relies solely on wind induced vent pipe draft and the convective flow of  warmed air upward in the vent to draw air from beneath the concrete slab     9 30 Working Level  WL   A unit of radon decay product concentration  Numerically  any  combination of short lived radon decay products in one liter of air that will result in the ultimate  emission of 130 000 MeV of potential alpha energy  This number was chosen because it is  approximately the total alpha energy released from the short lived decay products in equilibrium  with 100 pCi of Rn 222 per liter of air   See also the referenced document in paragraph 8 16      9 31 Working Level Month  WLM   A unit of exposure used to express the accumulated  human exposure to radon decay products  It is calculated by multiplying the average working  level to which a pe
30. n workers shall  be met     12 2 1 The contractor shall advise workers of the hazards of exposure to radon and the need  to apply protective measures when working in areas of elevated radon concentrations     12 2 2 The contractor shall have a worker protection plan on file that is available to all  employees and is approved by the PA DEP     12 2 3 The contractor shall ensure that appropriate safety equipment such as hard hats  face  shields  ear plugs and protective gloves are available on the job site during cutting  drilling   grinding  polishing  demolishing or other hazardous activity associated with radon mitigation  projects  The contractor shall ensure that all new employees have been informed about all  relevant portions of the company worker protection plan  All relevant portions of the worker  protection plan shall be reviewed with each employee at least once a year  Confirmation of  employees  knowledge of relevant portions of the worker protection plan should be recorded  with the employees  signature and date     12 2 4 All electrical equipment used during radon mitigation projects shall be properly  grounded  Circuits used as a power source should be protected by Ground fault Circuit  Interrupters  GFCI      12 2 5 When work is required at elevations above the ground or floor  the contractor shall  ensure that ladders or scaffolding are safely installed and operated     12 2 6 Work areas shall be ventilated to reduce worker exposure to radon decay products   d
31. radon system  Battery operated monitoring devices shall not be used unless they are  equipped with a low power waming feature     16 3 A system description label shall be placed on the mitigation system  the electric service  entrance panel  or other prominent location  This label shall be legible from a distance of at least  three feet and include the following information  indication that this is a radon system    Radon  Reduction System   the installers name  phone number  and PA DEP Certification Number  the  date of installation  and an advisory that the building should be tested for radon at least every  two years  In addition  all exposed and visible interior radon mitigation system vent pipe  sections shall be identified with at least one label on each floor level  The label shall indicate   that it is part of a radon reduction system and read    Radon Reduction System         16 4 The circuit breaker s  controlling the circuit s  on which the radon vent fan and system  failure waming devices operate shall be labeled   Radon System         21 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      17 0 POSTMITIGATION TESTING    17 1 After installation of an active radon control system  e g  SSD   the contractor should  reexamine and verify the integrity of the fan mounting seals and all joints in the interior vent    piping     17 2 After installation of any active radon mitigation system  the contractor should measure 
32. rson has been exposed by the number of hours exposed and dividing the  product by 170     10 0 GENERAL PRACTICES    The following general practices are required for all contacts between radon mitigation  contractors and clients     10 1 In the initial contact with a client  the contractor shall review any available results from  previous radon tests to assist in developing an appropriate mitigation strategy  The contractor  shall inform the client when it is determined that previous radon measurements were not  performed according to EPA protocols and recommend a retest be done     10 2 Based on guidance contained in  A Citizen s Guide to Radon  Second   Edition     paragraph 8 8  and the  PA Home Buyers and Seller s Guide  or subsequent revisions  of these documents  the contractor shall refer the client to the discussions of interpreting indoor  radon test results and the health risk associated with the radon level found in the building  The   Pennsylvania Consumer s Guide To Radon Reduction   paragraph 8 9  is an appropriate  reference for providing advice on actions to take to reduce indoor radon levels     10 3 When delays in the installation of a permanent radon control system are unavoidable due  to building conditions or construction activities  and a temporary system is installed  the  contractor shall inform the client about the temporary nature of the system  A label that is  readable from at least three feet shall be placed on the system  The label shall include a
33. s  Based on its evaluation  the US EPA may  initiate established Radon Contractor Proficiency program delisting procedures against those  contractors found to be in violation of these standards     6 4 Those provisions of the PA RMS that are considered to be mandatory are prefaced by the  term  shall   Provisions that are considered good practice but which are not mandatory are  prefaced by the terms  should  or   recommended      6 5 The PA RMS will be updated as necessary  and in response to technological advances and  field experience  The scope of the PA RMS will also be expanded when new revised mitigation  technologies have been demonstrated in other types of residential and nonresidential buildings     6 6 For areas of radon mitigation not covered by this standard  the contractor shall follow the  guidance outlined in the reference documents  See paragraph 8 0  and his her training obtained  in PA DEP approved radon mitigation courses     7 0 LIMITATIONS    7 1 Although the provisions of the PA RMS have been carefully reviewed for potential  conflicts with other regulatory requirements  adherence to the PA RMS does not guarantee  compliance with the applicable codes or regulations of any other Federal  state or local agency  having jurisdiction     7 2 Where discrepancies exist between provisions of the PA RMS and local codes or  regulations  local codes shall take precedence  However  where compliance with local codes  necessitates a deviation from the PA RMS  or a de
34. slab  a length of backer rod is  compressed into the opening around the pipe  Caulking is then applied to the space above the  backer rod and between the outside of the pipe and the slab opening  The purpose of the backer  rod is to hold the semifluid caulk in place until it sets or hardens  and act as a bond breaker     9 3 Block Wall Depressurization  A radon mitigation technique that depressurizes the void  network within a block wall foundation by drawing air from inside the wall and venting it to the  outside     9 4 CCA treated for ground contact  Chromated Copper Arsenate  CCA  applied at a rate of  0 4 Ib Cu Ft allows wood to be in ground contact  Lumber treated at a rate of 0 25 Ib Cu Ft is  not intended for ground contact     9 5 Certified  A rating applied by the PA DEP to individuals or firms that are authorized to  provide radon related services within the Commonwealth     9 6 Client  The person  persons  or company that contracts with a radon mitigation contractor  to install a radon reduction system in a building     9 7 Combustion Appliance  Any device which utilizes the ignition of a fuel to perform work  for a specific purpose including but not limited to heating  drying  cooling  and refrigeration     9 8 Combination Foundation  Buildings constructed with more than one foundation type   e g   basement crawlspace or basement slab on grade     6 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      9 9 Commun
35. tall a radon resistant drain as defined in paragraph 9 21     14 7 2 If condensate drains from air conditioning units terminate beneath the floor slab  the  contractor shall install a trap in the drain that provides a 3 to 6 inch trap of standing water  or  reroute the drain directly into a trapped floor drain or condensation pump     14 7 3 When a sump pit is the only system in a basement for protection or relief from excess  surface water and a cover is installed on the sump for radon control  the cover shall be recessed  and fitted with a trapped drain meeting the requirements of paragraph 9 21     14 8 HVAC Installation Requirements    14 8 1 Modifications to an existing HVAC system  which are proposed to mitigate elevated  levels of radon  should be reviewed and approved by the original designer of the system  when  possible  or by a licensed mechanical contractor     14 8 2 Foundation vents  installed specifically to reduce indoor radon levels by increasing the  natural ventilation of a crawlspace  shall be noncloseable  In areas subject to freezing  conditions  insulation  where necessary  shall be provided for to protect against freezing and  unnecessary energy loss     14 8 3 Heat Recovery Ventilation  HRV  systems shall not be installed in rooms that contain  friable asbestos     14 8 4 In HRV installations  supply and retum vents in the interior shall be located a  minimum of 12 feet apart  The exterior intake and exhaust vents shall be positioned to avoid  blockag
36. tems shall meet all of the following  requirements   1  be above the eave of the roof   2  be ten feet or more above ground level   3   be ten feet or more from any window  door  or other opening into conditioned spaces of the  structure that is less than two feet below the exhaust point  and  4  be ten feet or more from any  opening into an adjacent building  The total required distance  ten feet  from the point of  discharge to openings in the structure may be measured either directly between the two points or  be the sum of measurements made around intervening solid obstacles     14 2 9 When a radon mitigation system is designed to draw soil gas from a perimeter drain  tile loop  intemal or external  that discharges water through a drain line to daylight or a soak  away  a one way valve  water trap  or other control device should be installed in or on the  discharge line to prevent outside air from entering the system while allowing water to flow out of  the system     14 3 Radon Vent Fan Installation Requirements    14 3 1 Vent fans shall be designed specifically for radon removal applications and be  designed or otherwise sealed to reduce the potential for leakage of soil gas from the fan housing     14 3 2 Radon vent fans should be sized to provide the pressure difference and air flow  characteristics necessary to achieve the radon reduction goals established for the specific  mitigation project  Guidelines for sizing vent fans and piping can be found in the references 
37. the  suction in the system piping  Measurement of system airflow should also be performed to help  assess system performance  Finally  a pressure field extension measurement should be made at  the most distant point from a penetration  this can be done using either smoke or a  micromanometer  to assure that the system is operating as designed     17 3 Immediately after installation and activation of any active  fan powered  sub slab  depressurization or block wall depressurization system in buildings containing natural draft  combustion appliances  the building shall be tested for backdrafting of those appliances  Any  backdrafting condition that results from installation of the radon mitigation system shall be  corrected before the system is placed in operation   Procedures and a checklist for conducting  backdrafting tests are covered in the reference documents listed in paragraphs 8 11  8 12  8 13   and 8 14 and in paragraph 11 3      17 4 To provide an initial measure of effectiveness  the contractor shall ensure that a  short term radon measurement using an RMP listed test device and in accordance with EPA  testing protocols is conducted no sooner than 24 hours nor later than 30 days following  completion and activation of the mitigation system s   See the Radon Certification Regulations   Title 25  Chapter 240 for post mitigation testing options    17 5 To ensure continued effectiveness of the installed radon mitigation system s   the  contractor shall advise the client
38. ust  or other airbome pollutants  In work areas where premitigation levels have been greater  than 0 33 WL  66 pCi l  and where ventilation is impractical or where ventilation cannot reduce  decay product levels to less than 0 33 WL  66 pCi l   based on a short term test   the contractor  should ensure that respiratory protection conforming with the requirements in the NIOSH Guide  to Industrial Respiratory Protection is available on the job site   See paragraph 8 17       12 2 7 Where combustible materials exist in the specific area of the building where radon  mitigation work is to be conducted and the contractor is creating any temperatures high enough  to induce a flame  the contractor shall ensure that a fire extinguisher suitable for type A  B  and  C fires is available in the immediate work area     12 2 8 Pending development of an approved personal radon exposure device and a protocol for  its use  the contractor shall record employee exposure to radon at each work site  based on   1   the highest pre mitigation indoor radon or working level measurement available  and  2  the time    12 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      employee s are exposed  without respirator protection  at that level  See paragraph 12 2 6     Note  This approach is not intended to preclude the alternative use of on site radon or radon  decay product measurements to help determine actual exposure   Consistent with OSHA  Permissi
39. viation is required for research or other  purposes  the PA DEP requires contractors to give written notification of these deviations prior  to initiation of work     7 3 The PA RMS is not intended to be used as a design manual  and compliance with its  provisions will not guarantee reduction of indoor radon concentrations to any specific level     3 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS      7 4 The PA RMS shall not apply to radon mitigation systems installed prior to its effective  date  However  if a radon mitigation system is found that does not comply with current  standards  the contractor shall recommend in writing to the client that the system be upgraded or  altered to meet current standards  The contractor shall obtain prior approval from the client  before implementing any of the contractors written recommendations     7 5 Because of the wide variation in building design  size  operation and use  the PA RMS  does not include detailed guidance on how to select the most appropriate mitigation strategy for  a given building  That guidance is provided in the documents referenced in paragraphs 8 2  8 3   8 4  and 8 5     7 6 The provisions of the PA RMS are limited to proven technologies and methods   Publication of this standard is not intended  however  to inhibit research and evaluation of other  innovative radon mitigation techniques  When such research is conducted  a performance  standard shall be appli
40. ween the basement and the first floor    2  Tum off all natural draft appliances      3  Close fireplace and wood stove dampers     10 of 24    Pennsylvania Department of Environmental Resources  DER    Radon Mitigation Standards  RMS       4  Tum on all exhaust fans and any forced air distribution fans    5  Wait at least 5 minutes after natural draft appliances have been tumed off    6  To begin a test for actual spillage of flue gases  tum on the appliance being tested      7  Using either a chemical smoke or a carbon dioxide gas analyzer  check for flue gas spillage  near the vent hood after appliance has been running for five minutes      8  Repeat steps  5  through  7  for each natural draft combustion appliance being tested for  backdrafting  Be sure to tum off any combustion appliances that feed into the same chimney as  the natural draft appliance being tested  Seasonal and extreme weather conditions should be  considered when evaluating pressure differentials and the potential for backdrafting     If spillage is confirmed from any natural draft combustion appliance  clients shall be advised of  the backdrafting condition and that active  fan powered  radon mitigation systems cannot be  installed until the condition has been corrected  The contractor should advise the client to contact  an HVAC contractor if correcting an existing or potential backdrafting condition is necessary    See paragraph 17 3 for post  mitigation backdrafting test      11 4 If installation of
41. y occuning radioactive element  Rn 222  which exists as a gas and is  measured in picocuries per liter  pCi L      9 21 Radon Resistant Drain  A floor drain that has a check valve that minimizes air flow if  the drain trap dries up or the trapped drain has an automatic supply of priming water     9 22 Radon Decay Products  The four short lived radioactive elements  Po 218  Pb 214   Bi 214  Po 214  which exist as solids and immediately follow Rn 222 in the decay chain  They  are measured in units of working levels  WL      9 23 Reentrainment  The unintended re entry into a building of radon that is being exhausted  from a radon mitigation system     9 24 Soil Gas  The gas mixture present in soil which may contain radon     9 25 Soil Gas Retarder  A continuous membrane or other comparable material used to retard  the flow of soil gases into a building     9 26 Stack Effect  The overall upward movement of air inside a building that results from  heated air rising and escaping through openings in the building envelope  thus causing indoor air  pressure in the lower portions of a building to be lower than the pressure in the soil beneath or  surrounding the building foundation     9 27 Submembrane Depressurization  A radon control technique designed to achieve lower  air pressure in the space under a soil gas retarder membrane laid on the crawlspace floor  relative  to air pressure in the crawlspace  by use of a fan powered vent drawing air from beneath the  membrane  Complete sea
    
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