Soil Gas - Hazards and Solutions

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Information about Soil Gas - Hazards and Solutions

Published on May 27, 2008

Author: donwhite



Monitoring of hazardous soil gases and use of the ECHO System in basement alleviate soil gas problems.

Indoor Air Technologies toll free (800) 558-5892Soil gasSoil gas -- hazards and solutionshazards and solutionsRXJODV 6 :DONLQVKDZ 3K 3(QJ•Radon monitorgives real timereading. Hourlyvariations re-quire 4 days toobtain goodpicture of levels.•Lower explosivelimit (LEL:methane,pentane...) andhydrogen sulph-ide (H2S) mon-itor organicmatter decaygases.LEL, H2S monitorRadon monitor

VOC samplingidentifies varioussoil gas problemsincluding toxicwaste offgasingand microbialoffgasing.Sampling pump with sorbent volatileorganic compound sampling tube3 media VOC sorbent tube

Smoke pencilUsed to identifyair flow directionsand approximatevelocities.MicromanometerUsed to measurepressure differ-ences (+/- 0.1 Pa)and air velocities.Micromanometer for measuringflows and pressure differencesSmoke pencil for identifyingair currents

SOIL GASESMethaneColorless, odorless, explosive. Produced bydecaying vegetable matter. It is the maincomponent of natural gas.Hydrogen sulphideColorless, very poisonous gas produced bydecaying animal or vegetable matter.Dichloromethane (methylene chloride)Chloroform-like odor. Solvent. Soil gasoriginating in garbage. Formed by thecombination of methane and chlorine. Thechlorine is leached from paper. Affects theCNS. Causes anoxia.• methane• hydrogensulphide• methylenechloride• gasoline VOCs• radon• pesticide toxins,Cl, HCn…• microbial VOCs,ketones, alcohols,esters, aromatics...

SOIL GASES cont’dGasolineSweet odor, explosive. Causes sensory irritationand affects the CNS.RadonColorless, odorless, radioactive, gas. Causes 5%of lung cancers. Exposure to 4 pCi/l equivalentto smoking 2 packs of cigarettes per day.PesticidesHighly toxic.e.g. chlordane C10H6Cl8e.g. hydrogen cyanide (HCN) bitter almondsmell - irritant, anoxiae.g. phosgene (Cl2CO) smokers exposed topesticides at risk - irritation, anoxia, pulmonaryedema.• methane• hydrogen sulphide• methylenechloride• gasoline VOCs• radon• pesticide toxins,Cl, HCn…• microbial VOCs,ketones, alcohols,esters, aromatics;toxic propagules

SOIL GASES cont’dMoldMicrobial VOCs are produced during thegrowth of a wide range of bacteria and fungi,forming complex molecules of alcohols,aldehydes, esters, hydrocarbons, and aromatics.Earthy odours are sometimes markers. MVOCeffects include nausea, malaise, stuffiness andwheezing.Microbial propagules (e.g. spores, NSI) fromsoil (e.g. crawl space; construction) can betoxigenic. e.g. Penicillium auranteogrisium(kidney disease), Penicillium brevicompactum(teratogenic, immunosuppressive), Stachybotryschartarum (pulmonary haemorrhage in infants,lung disease in adults)• methane• hydrogen sulphide• gasoline• radon• pesticides• microbialmicrobial VOCs,ketones, alcohols,esters, aromatics;toxic propagulesFungal colony

Case History # 1Service station restaurant gasolinefumesRestaurant maxLEL* TVOCApril 28Complaints of headache 65% 125 mg/m3June 2Blower installed to exhaustsump pit and weeping tile14 mg/m3June 4 3 mg/m3* Lower explosive limit, LEL (pentane equivalent)low alarm 10%high alarm 20%ProblemGasoline fumes were aboveLEL high alarm level in airentering a service stationrestaurant. Venting abovea sump pit where levelswere highest did not solvethe problem.SolutionThe sump pit was sealedtightly and then exhaustedunder pressure. This causedthe under-ground fumesfrom a leaking tank to bedrawn into weeping tilewithout entering thebuilding.

Case History # 2Basement petroleum fumes•A PID identified petroleum fumes on one of thebasement foundation block walls, with highestreadings (TVOC =20 mg/m3) in an adjoining interiorabutment block wall.•Source possibilities included heating oil used in thefurnace, possibly leaking from a line passing underthe slab, and leaking gasoline from an undergroundtank at a nearby gas station up the hill from the house.•GC/MS headspace analysis vs. basement air findingsidentified the source as gasoline using benzene as amarker.ProblemStrong petroleumfumes were noticedin a bungalow base-ment. The fumeswere entering via aninterior block wallbracing the peri-meter block wall.SolutionThe block wall wassealed and exhaust-ed outdoors continu-ously by a blowerfor several monthsuntil the odordisappeared.

Case History # 2 cont’dBasement petroleum fumes• It was concluded that the fumes originated fromgasoline discarded from a lawn mower a few weeksearlier in a depression in the lawn (TVOC = 30mg/m3 in the soil here using PID). This depressionmarked a break in an old underground water drainleading from the basement. House stack effect drewair up the pipe to the basement.ProblemStrong petroleumfumes were noticedin a bungalow base-ment. The fumeswere entering via aninterior block wallbracing the peri-meter block wall.SolutionThe block wall wassealed and exhaust-ed outdoors continu-ously by a blowerfor several monthsuntil the odordisappeared.

Case History # 3Basement bedroom toxic moldFungal aerosols March 11CFU/m3 Species in order of coloniesBasement bedroom 175 Penicillium auranteogrisiumPenicilium brevicompactumpenicllium sp.Cladosporium, NSICrawl space TNTC Penicillia, Aspergilli,Stachbotrys chartarumProblemConcern about moldexposure of adaughter whosebedroom was in aranch-style backsplit/bungalowbasement led tofungal investigation.It identifiedtoxigenic species inthe bedroom air.The source was anearby crawl spacewith a soil floor.SolutionThe crawl spacewas sealed anddepressurized with acontinuouslyoperating blowerexhausting to theoutdoors.

Case History # 4Radon exposureProblemRadon levels in anOttawa RockcliffePark house basementexceeded 4 pCi/l.This exposure isequivalent to smoking2 packs a day interms of lung cancerrisk.SolutionThe basement wasfinished with theECHO System. Itforms a ventilatedand depressurizedcontinuous subfloorand perimeter studwall barrier to radonand any other soil gasentry. 0:00Date, time of dayRadon,pCi/lVideo room Wrkshp Wi.ce Living rm Video roomECHO blowers on ECHO blowers onECHOblow ersoffPrimaryECHOblow eron ECHOblowersoff2ndaryECHObloweronAction level = 4 pCi/l

ProblemSewer smell inbasementSolution• Sump sealed andexhaustedcontinuouslyoutdoors with 65watt blowerCase History #6Store basementStaff and patrons complained of sewer smell in thebasement of the store.Recommended that sump be sealed and exhausted by a110 CFM blower with a speed control.At 0,.5 Pa negative pressure, some sewer smell stillobserved in the basement.Sump was better sealed, so depressurization above 2Pa. Problem solved.

ECHO System basement finishingThe ECHOSystem preventssoil andenvelope gasesand vapourentry bydepressurization- not by aircirculation.It removesleakage waterby drainage andevaporation.

Drained &depressurizedwall & sub-slabDrained &depressurizedwall & Sub-floorDepressurizedwalls and sub-floors preventfinishedbasement soilgas entry

Crawl space exhaustCrawl spaces canbe strong sourcesof mold emissionsand soil gases intothe living space.Exhaust ventilationdehumidifies and warms thespace with house air, while itdepressurizes it.

Sub-slab depressurizationProblemSoil gas entry through theslab cracks and openings.One solutionSub-slab depressurization• provided there is agravel layer under slab• the foundation under-ground has fairly air tightboundaries.• SSD does not preventsoil gas entry throughfoundation wall cracksand cavities.• Minimize exhaust rate toavoid foundationproblems (frost heave,soil drying).

Soil Gas HazardsSummary•Lung cancer - radon gas (concern in perhaps 1/5 houses, ? schools)• radon is present in all soil• radon levels cannot be predicted from site location alone• foundations on stone are high risk•Toxic effects: irritant, CNS affects, allergenic effects, kidneydisease, cancer, anoxia...• toxigenic molds e.g. S. chartarum, P. auranteogrisum in crawlspaces• pesticides used in control of insects, rodents e.g. Cl, HCn...• CNS effects, explosions• underground gasoline leaks• waste disposal• natural gas leaks• contaminated fill• wet organic soil

Soil Gas SolutionsSummary• Sump pits•seal and power vent outdoors, depressurizing weeping tilearound perimeter of foundation• Slab•seal and power vent sub-slab air outdoors• needs gravel under slab• 50-150 cfm exhaust rate• does not eliminate foundation wall entry• Slab and foundation walls• use the ECHO System: seal sub-floors and perimeter studwalls against foundation and power vent cavity air outdoors•10 - 100 cfm exhaust rate, depending on system tightness• coincidentally solves finished basement mold problem• coincidentally provides leakage protection• coincidentally provides filtered house ventilation air• Crawl spaces• seal envelope and power vent outdoors• coincidentally dehumidifies crawl space

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