Evaluation of Airborne Hazards in the Workplace Flashcards
What is the difference between a grab sample and an integrated sample?
Grab sample - one time sample
Integrated sample - samples taken over a period of time (more usual since we compare to TWA)
What is time weighted average
concentration of airborne hazard present during 8 hours
Why are TWAs important?
Exposure may not be consistent throughout the day
Someone could be moving around, not near the hazard
How have trends changed in terms of sampling devices?
Used to sample only, now sample and analyze
What do sampling devices typically measure? what units?
concentration (how much dust per volume) in mg/ m3 or ug/ m3
What is the difference between velocity and fowrate?
Velocity measures how fast air moves
Flowrate - volume that moves expressed over time (CFM)
What is the equation for TWA?
(C1T1+C2T2+CnTn) / 8
C = concentration T = time
What should you refer to for proper sampling techniques?
NIOSH Manual of Analytical Methods (NMAM)
What is the sampling “train”
Inlet –> collector and meter –> outlet
Describe personal sampling
- needs to be as close to the breathing zone as possible
Which is better for determining the concentration that a worker is getting - air sample or personal sample
personal sample
How does air sampling work?
place a monitor somewhere in room and it sits there
What are considerations when sampling?
- Is sample representative
- how many samples?
- who to sample
- when to sample
- efficiency
- stability
- safety
- field ease
Describe the set up of the filter cassette
specialized cassettes (collect a specific aerosol or dust, ie asbestos). Connected to tubing and a pump with medium flow rate sampling pump (2LPM)
How do you determine the concentration of the substance with a filter?
Weight the filter before and after sampling
What is the benefit of contour maps?
- good for area samples
- look at highest concentrations in an area to establish the main sources
Describe the direct reading aerosol samplers?
track dust - PM1, PM2.5, PM10, respirable, total PM size fractions
What is PBZ?
Personal breathing zone
What are cyclones used to measure?
Aerosol sizing
What is the most common analysis for aerosols?
Gravimetric (weigh filter before and weigh filter after)
What types of aerosol analysis can be used?
- gravimetric
- chemical analysis
- Microscopy
- Culture
What would microscopic aerosol analysis be used to measure?
Asbestos, microorganisms
What are some example of microbiological analysis?
- PCR
- Fluorescence
- ELISA
What should you test for in confined spaces?
Gas sampling
- oxygen deficiency
- % LEL
- Specific gases (CO, O3, H2S)
When should you sample confined spaces?
Before entering
What can charcoal tubes be used to sample?
vapors- like benzene
What equipment is used for aerosol sampling?
1) Personal Sampling Pump (medium flowrate)
2) Filter Cassettes
3) Cyclones (for aerosol sizing)
4) Direct Reading Aerosol Samplers (like the DustTrak)
How do you test for aerosols in ducts?
- Isokinetic sampling?
- Biosampler, like Anderson Biosampler
What equipment can be used for gas sampling?
- Sampling pump (low flowrate)
- charcoal tubes- different tubes for different substance
- direct reading instruments
What labs should be used for analysis?
Labs credentialed by the AIHA
What analysis is used for metals?
Atomic absorption
What analysis is used for organics?
Gas chromatography
What are the different types of lab analysis?
- atomic absorption
- gas chromatography
- electron microscopy
- mass spectroscopy
- Photometry
How can you calibrate a direct reading sampler
Zero gas or zero aerosol
Known gas concentration
What way does the air move between the calibrator to the pump?
From calibrator, through filter cassette, to the pump or calibrator to cyclone to pump
Inhalable?
aerosols that can be inhaled (<100 um)
Respirable?
aerosols that can enter the pulmonary region (<10 um)
Thoracic?
aerosols that can enter the tracheobronchi region- <40 um
TWA
Time weighted average (concentration maximum averaged over 8 hours)
STEL
Short term exposure limit (concentration limit for 15 minutes)
REL
Recommended exposure limit- determined by NIOSH
PEL
Permissible exposure limit- legally binding by OSHA
TLV
Threshold limit value- ACGIH stanard
NMAM
Niosh manual for analytical methods
What are the parts of a sampling pump?
Inlet - pulls air in
Outlet - pushes air out
What mode are most pumps used in?
Suction mode
What pumps run on an alternating current and require an electrical outlet?
high flowrate pumps
What is the most common pump used in industrial hygiene?
Personal air sampling pump
What current do personal air sampling pumps run off of?
DC- direct current, use rechargeable batteries which take 8-16 hours to charge
Are personal sampling pumps safe to use in explosive environments?
Yes- totally enclosed and spark free
What is the most common medium and analysis for aerosol sampling?
Filters and gravimetric
How does gravimetric analysis of a filter work?
Weigh the filter before and after and the difference in weight is the weight of the aerosol. Net weight/ air volume gives the concentration.
What must be constant at both gravimetric weighings?
relative humidity
FIlters that are already weighed
matched weight filters
How does gravimetric analysis of pre-weighed filters work?
Measure difference in weight between used filter and blank filter directly from same box
What resource specifies the type of filter to use for each aerosol?
NMAM
What are the filters held in?
Filter cassettes
Why is there a backup filter in the filter cassette?
to prevent destruction by movement of air
How do you minimize sample lises?
Make sure the cassette is well sealed
What are the types of cassettes?
closed face- very small opening (minimizes loss of sample)
open face- large opening
Which cassette type is required for microbiological analysis?
open faced
What is the equation for flowrate?
Flowrate = volume/ time
What devices measure flowrate?
Flowrate meters
What are the simple/ more complext flowrate meters called?
primary- simple
secondary- more complex (only secondary if it holds a calibration well)
What is the concern with more complex flowmeters?
they do not hold calibration well
Describe the relatioship between the flowmeter and the pump
Some flowmeters built into the pump while others are put in the sampling train upstream from the pump
Describe the sampling train for a flowmeter
air enters –> collector –> flowrate meter –> pump –> air exits
Describe the calibration train
air enters calibrator –> collector –> flowrate meter –> pump –> air exits
How close a measurement is to the true value
accuracy
What is the calculation for % error. what does it help to measure
(Calibraory avg reading (LPM) - Device Avg reading) / calibratory avg reading * 100
Helps to measre accuracy
What is the calculation for estimate of accuracy?
100% - % error
Need to calculate the % error first
indicates how close replicate values are to each other
precision
What equation is used to measure precision?
RSD- relative standard deviation
How do you determine from the RSD if the reading is precise?
The lower the RSD, the more precise the measurements
What is the equation for the RSD?
Standard Deviation/ mean
What is the difference between replicability and reproducibility?
replicability- within analyst’ RSD (ie 4 students repeat the same measurement)
Reproducibility- among laboratories’ RSD
What is the TWA for:
8AM -10 AM : 3 mg/m3
10AM - 4PM : 2mg/ m3
((3mg / m3* 2 hrs) + (2 mg/ m3*6 hrs)) / 8 hrs= 2.25 mg/ m3
How do detector tubes/ charcoal tubes work? What type of analysis?
Have granules that absorb gas (use arrow to make sure air is moving the correct way)
Connect tye to black filter side (sucks the air through)
Break tips before- when done, cap
Ship to the lab- analytical
Are you supposed to weigh the support pad with the filter?
No
What is the sample train between the filter and support pad?
Air is sucking so inlet –> filter pad –> support pad –> outlet
What is the purpose of the cyclones?
It removes all aerosols that are larger than respirable size
What calibration do you use for particle counters?
zero calibration
What is the particle counter that we have in the lab?
Dustrak
How can you prevent impact of relative humidity in gravimetric analysis?
Let the filters sit 24 hours before weighing before sampling and 1 hour after sampling
