Basic air sampling knowledge
Employers are responsible for their workers’ safety. Whether you self-perform your air sampling or hire an industrial hygienist to do it, knowing how sampling works will ensure your workers aren’t exposed to hazardous atmospheres. Six things you should be familiar with are:
- Process, and
Understanding some of these essential things will provide you a general understanding of how sampling works. You will be more confident when making decisions about protecting your workers or interacting with an industrial hygienist.
Methods for air sampling
There are five primary sampling methods:
- Grab sampling — you’re “grabbing” a sample of air using direct reading equipment or a known volume of air in a container commonly called a Tedlar® bag that is sent to a laboratory for analysis.
- Personal sampling — here, an employee wears a sampling device. A pump draws air through a filter for sample collection. The filter media is removed from the pump and sent to a laboratory for analysis. Personal sampling is a standard method used to assess personal worker exposure, such as lead, hexavalent chromium, or silica.
- Area sampling — is another common sampling method and uses the same equipment as personal sampling does. The difference is that the pumps aren’t clipped to a worker with area sampling, and the filter media isn’t placed in the worker’s breathing zone. Instead, it’s placed in the general area where workers are working.
- Integrated sampling — this requires sampling the worker’s breathing zone using personal sampling methods. Several samples are usually taken to determine the worker’s exposure over an 8-hour time-weighted average.
- Direct reading — this method uses calibrated equipment to take direct samples and provides an instant reading that a competent person can analyze to determine workers’ exposure level. The most familiar example of using direct-reading equipment is a confined-space monitor.
All the sampling methods above can be done without guidance from an industrial hygienist, except for one. If you’re going to use grab sampling, I recommend hiring a consultant to assist you because it can get technical. But the other four are common enough that how-to instructions for setting up the sampling equipment are widely available from the manufacturer, including step-by-step videos online. You’ll send the filter media to a laboratory for testing, and they’ll send you the results.
Media and calibration
I’d rent my pumps and filter media directly from the lab. I didn’t need to worry about its maintenance or calibration. The lab would send me a heavy-duty case with everything I needed in it to start sampling. You could buy your equipment — but it’s not cheap. Most workplaces already have confined-space monitors. Sampling pumps are easy to maintain, and you can buy filter media from a supplier. If you don’t have the budget, though, it’s convenient to rent everything from the lab to avoid the hassles of ownership.
Volume and process for air sampling
Determining how much sampling and what processes to use is simple once you can pinpoint one to follow. I recommend following either NIOSH, OSHA, or the laboratory you’re going to send your filter media to for analysis. Choose a laboratory that has been accredited by the American Industrial Hygiene Association (AIHA). An accredited lab will analyze your media following a nationally recognized process, usually either OSHA or NIOSH. My preference was always to follow OSHA’s protocols. The NIOSH Manual of Analytical Methods is a bit technical, whereas OSHA’s guidance is written for employers and is a bit more reader friendly. As mentioned, you can use your lab’s protocols too.
Employers should use a chain-of-custody form to track the sample media from the point of collection in the workplace to the laboratory. Recordkeeping can be particularly useful if you’re asked questions by OSHA or in any legal proceeding. The person at your workplace collecting the samples will initiate the chain-of-custody. Each person who handles the media will sign the form until it’s mailed to the laboratory. When the lab sends you results, they will send you the original, completed copy of the chain-of-custody. Make it a habit of photocopying this form before sending it to the lab in case it gets lost in the mail.
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