1 Air Monitoring: Back to Basics. 2 Air monitoring is commonly performed on Hazardous Waste Operations (HazWoper) sites There is more to air monitoring.

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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?