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Transcript of 1 Air Monitoring: Back to Basics. 2 Air monitoring is commonly performed on Hazardous Waste...
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Air Monitoring:Back to Basics
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Air monitoring is commonly performed on Hazardous Waste Operations (HazWoper) sites
There is more to air monitoring than “waving a wand”
You need a strategy in order to have meaningful results
Air monitoring is a generic term – often used for both air monitoring & air sampling
The focus today is on air monitoring – however both may be needed for your project!
Overview
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Monitoring vs. Sampling
Air Monitoring Direct reading
instruments, “real time” data
Compared against action levels
Typically hand-held Usually performed
for short duration Typically performed
by URS field crew – Site Health and Safety Officer
Air Sampling Collects air sample,
analyzed by lab Compared against PELs,
STELs or Ceiling Limits Personal sampling
pump & collection media
Usually collected over 8 hour shift
Typically performed by Industrial Hygienist or other specially trained individual
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Air Monitoring
29 CFR 1910.120 states:
“Air monitoring shall be used to identify and quantify airborne levels of hazardous substances in order to determine the appropriate level of employee protection needed on site”
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Key Elements of a Monitoring Plan
Define site activities and discrete tasks
Identify potential airborne hazards for each task (metals, hydrocarbons, CO, H2S, etc.)
Identify who should be monitored
Establish air monitoring objectives
Select equipment
Interpret data
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Defining Activities & Tasks
Review project documents such as the project proposal, contract, scope of work, and/or specifications, & responsibilities
Discuss field activities with Project Manager & field staff
Develop detailed job safety analysis
Identify who will perform the task and the approximate time needed to complete the task
Field activities and tasks must be clearly defined.
How to define field tasks?
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Identifying Potential Hazards
The most common atmospheric hazards include:
Toxic substances (gases, vapors, particulates)
Oxygen deficient (<19.5% O2)
Flammable (gases, vapors, particulate, or oxygen enriched)
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Identifying Potential Hazards
Also consider :
The volatility of site contaminants (methylene chloride vs. creosote) and outside temperature
Products used on site (paints, cleaners, welding supplies, sample preservatives)
Materials removed or disturbed on site (lead paint, asbestos insulation, etc.)
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Scenario #1
Answer: Not likely, because:
No expected contaminants
Work performed in the open
No intrusive activities
“Up-gradient well” indicates good knowledge of the site.
A URS field team will be collecting groundwater samples from established, up-gradient monitoring wells. Is air monitoring needed?
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Scenario #2
URS is contracted to excavate and remove buried drums containing pesticide waste. Subcontractors will operate excavation equipment and haul waste off-site. New housing developments and a grade school borders the site. Is air monitoring needed?
Answer: Absolutely!
And the monitoring program will likely be complex and costly.
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Identifying Who Should be Monitored
Monitoring is likely needed for workers who are:
Closest to the “source” of contaminationPerforming tasks that generate airborne
contaminants (painting, welding, sand blasting, etc.)
Entering confined spaces
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Scenario #3 A team is contracted to install ground water monitoring wells down gradient from a former retail gas station. A drilling subcontractor will install the wells. Who should be monitored?
Answer: It is often responsible for the drilling crew. The breathing zone of the drillers helper would be the best location for monitoring.
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Common Monitoring Objectives
Assess worker exposures to airborne contaminants
Establish level of respiratory protection
Evaluate fire/explosion hazards
Evaluate effectiveness of engineering controls
Evaluate off-site migration of airborne contaminants
Remember – certain regulatory standards (e.g. asbestos) mandate air sampling.
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Most commonly used for:Flammable or explosive atmospheresOxygen deficiencyVolatile organics Nuisance dusts Radiation
Direct Reading Instruments
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Direct Reading Instruments
Advantages Readings displayed
quickly (within seconds)
Durable Portable Easy to use
Disadvantages Often not specific May have limited
detection range Cross-sensitivity Can be temperature
& moisture sensitive Can’t be used for
most metals, asbestos, silica or unknowns
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What is the most important thing in gas detection when using Direct-reading instruments?
Proper Calibration!
Without a clean zero gas and an accurate verified calibration standard - there is no point in doing any gas detection.
Calibration
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Calibration
Calibrate per manufacturer recommendations
Check calibration in field every dayRecord calibration results & keep in
project file
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Photoionization Detectors - (PIDs) Uses ultraviolet light to ionize molecule. Primarily used for organic vapors (particularly BTEX)
- certain instruments use a benzene chip Ionization potential (IP) of lamp must exceed IP of
molecule Lamps typically range from 9.5 eV to 11.7 eV Response is relative to the response of the
calibration gas Limitations include:
Cross sensitivities, Lack of specificity when multiple compounds are present, Impacted by high humidity
Key manufacturers include: HNU, Photovac, RAE Systems, MSA
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Flame Ionization Detectors - (FIDs)
Uses hydrogen flame to ionize molecules
Ionization range is higher than PIDResponse is relative to the
concentration of the calibration gasLimitations include:
Shipping hydrogen gas More complex operation than PIDs Sensitive to methane
Manufacturers include: Foxboro, Photovac
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Combustible Gas Indicators - (CGIs)
Normally combine % oxygen and % Lower Explosive Limit (LEL) in one monitoring device
LEL sensor requires adequate oxygen; always check oxygen first
Measures “percent of” the LEL
LELs typically range from 0.8 to 6%
Action level of 10% to 25% of LEL to evacuate/stop work
Remember to use intrinsically safe instruments in flammable atmospheres.
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Oxygen Meters
This test is conducted first since it may affect the accuracy of other meters/sensors
Sensors have a shelf life of 1-2 years
Acid gases or high CO2 may poison the sensor and shorten the instrument life
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Oxygen MetersOxygen deficient atmospheres are the
#1 cause of confined space fatalities. Oxygen enriched > 23.5% O2
Normal atmosphere 20.8% O2
Oxygen deficient < 19.5% O2
IDLH* < 16.0% O2
* Immediately Dangerous to Life and Health
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Colorimetric Detector Tubes
Pump draws air through chemically treated tubes. The contaminant reacts with the chemical indicator to produce a color change or stain.
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Colorimetric Detector TubesAccuracy of ± 25%Limitations include:
Cross sensitivities Temperature extremes Difficulty in determining
stain length Short duration sample time
Check pump for leaks prior to use with an unbroken tube
Carefully read the directions for the specific tube you are using (e.g. number of pump strokes, color change, flow direction)
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Aerosol (Dust) Monitors
Uses light scattering to measure concentrations of particulates
Reads out in mg/m3
Not specific - measures total dust or respirable dust, depending on the unit
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Other Direct Reading Instruments
Hydrogen sulfide meter
Carbon monoxide meter (H2S & CO are usually part of 4 way meter)
Mercury vapor analyzer
Radiation detectors
Portable gas chromatograph
Ammonia detector
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Interpreting the Data(What does it all mean?)
Direct reading instruments are essential field equipment
Displays are generally easy to read and appear to be very precise
But, the data is meaningless unless there is an action level that was developed based on the chemicals of concern and the equipment response.
Do not confuse soil/water concentrations of the contaminants with airborne concentrations and action levels.
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Action LevelsAction Levels are threshold readings on a
direct reading instrument that, if exceeded, require an action (such as upgrading PPE or evacuation)
Documented in Project Health and Safety Plans and are based on: Chemicals of concern Exposure limits (such as PELs & TLVs) Type of instrument Relative response
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Action Levels
Action levels should be:Simple, clear & real-time Based on compound with lowest
exposure limit (when dealing with multiple compounds)
Less than exposure limit to compensate for instrument accuracy (safety margin)
Based on instrument that will measure chemicals of concern in range of exposure limits
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Action Levels - Example Table
Action Levels for Intrusive Activities
Monitoring Equipment
Sampling
Result/Observation
Action
PID (10.6 eV lamp) >1 ppm Continue to monitor with PID; monitor with benzene chips.
Benzene detector chip (with CMS device)
<0.5 ppm Continue to monitor with PID.
0.5 ppm, <25 ppm Upgrade to Level C. Continue to monitor with PID.
25 ppm Stop work; evacuate area and contact HSM.
PID (10.6 eV lamp) >1 ppm, 25 ppm; IF no benzene detected
Continue to monitor with PID.
>25 ppm, 250 ppm; IF no benzene detected
Upgrade to Level C. Continue to monitor with PID.
>250 ppm Stop work; evacuate area; contact HSM.
Hydrogen sulfide monitor
2.5 ppm Stop work; evacuate area; contact HSM.
MiniRam Dust Monitor
>15 mg/m3 Use dust control measures until dust is controlled. If dust cannot be controlled upgrade to Level C.
Observation Workers enter sheds or utility buildings where rodents may have nested; and workers may disturb nesting materials or rodent droppings.
Upgrade to Level C.
Observation Workers exhibit symptoms of chemical exposure
Stop work. Evacuate area and contact the HSM.
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Important Terms
Sensitivity – Ability of an instrument to detect the material in the range of interest.
Accuracy – How close the instrument readout is to the actual concentration.
Relative Response – Instrument response to a chemical of concern relative to the response to the calibration gas.
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Important Terms
Parts per million (ppm) – Parts per million by volume in air; primarily used for gases and vapors.
Examples of OSHA PELs:Phosgene = 0.1 ppmHydrogen sulfide = 20 ppmToluene = 200 ppm
100% = 1,000,000 ppm
1% = 10,000 ppm
.01% = 100 ppm
.0001% = 1 ppm
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Important Terms
Milligrams per cubic meter (mg/m3) – Milligrams of contaminant per cubic meter of air; used for particulates, dusts, mists and fumes. 1 mg/m3 = 1000 µg/m3
.1 mg/m3 = 100 µg/m3
Examples of OSHA PELs:Arsenic = 0.01 mg/m3 or 10 µg/m3
Lead = 0.05 mg/m3 or 50 µg/m3
Nuisance dust = 15 mg/m3 or 15,000 µg/m3
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Understanding the Data - Some Guidelines
“Zero” does not necessarily mean “clean”. Possible reasons for “zero” readings: Instrument is not working Concentration of compound is below the
detection limit (sensitivity) Instrument responds poorly (or not at all) to
the compound of interest Compound of interest is not volatile The area is actually “clean”
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Understanding the Data - Some Guidelines
Readings displayed may not be the actual concentration. Possible reasons include: Relative response - Instruments rarely have
a 1:1 response to a particular compound. Check user manual for response factors.
Multiple compounds - instrument may be picking up a variety of compounds, each with it own response factor or there may be an interference.
Response time - instruments may take several seconds to respond. If survey is too quick - may not pick up “hot spots”.
Instrument specificity - no single instrument can detect all airborne contaminants. Check user manual for specificity.
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Reading may not indicate actual exposure risk. Possible reasons include: Other routes of exposure - such as dermal
exposure (particularly heavy organics such as creosote, PCBs, and some pesticides).
Reading not taken in worker breathing zone - actual risk may be higher or lower depending on where reading is taken.
Multiple contaminants - possible additive or synergistic effects.
Individual sensitivity - exposure effects can vary greatly from person to person.
Understanding the Data - Some Guidelines
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Recording the Data
Record data in field log book or other suitable form.
Download or print out data if possible. Record calibration checks and “zero”
readings.Maintain records on site while project is
active; place in project file when project is finished.
Can’t prove the monitoring was conducted unless the data is recorded and retrievable.
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Review Scenarios
1. You’re the PM on a job involving the cleaning and dismantling of above ground gasoline storage tanks. You have a plan and equipment for monitoring organic vapors. OSHA arrives and requests to see your exposure control plan and air sampling data for Lead (tanks were painted with lead based paint - oops).
What went wrong?
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Review Scenarios
2. You’re the PM on a job involving the excavation and removal of soils impacted with BTEX compounds. You have a plan and equipment for monitoring organic vapors. Employees are complaining of strong odors, getting headaches, and feeling sick but the PID is reading below the action level.
What’s going on?
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Review Scenarios
3. You’re preparing a proposal for the excavation and removal of hundreds of drums of pesticide residue buried in an old, industrial landfill. What considerations do you need to make for air monitoring?
Who do you go to for help?