By Ayisha Malik, EMEA
Why you should measure air quality for inhalable contaminants
When working in certain industries, occupational health and safety (OHS) becomes a primary concern as a lot of chemicals and materials that are safe to work with can contribute towards potentially life-threatening illnesses when inhaled.
Outdoor, indoor and workplace air contains dust particles, vapours, fumes, and bioaerosols; including materials such as silica, asbestos, coal, and pesticides that can contribute towards issues like lung disease. When you breathe in potentially harmful substances, it is known as “inhalation exposure.” The risk of respiratory illnesses from this type of exposure depends on the type of contaminant, the length of exposure, and the location of where it lands in the lungs.
Occupational lung diseases can develop because of repeated, long-term exposure or following a single exposure event to a high volume of a particular agent. Avoiding these hazardous contaminants can prevent health issues from developing in the first place. Additionally, minimising exposure can also help reduce the risk of illnesses and even reverse certain conditions. Therefore, it is important to monitor and manage not just the overall air quality within the workplace, but also to look at the exposure profiles for individuals stationed at different areas of the site. Routinely testing workplace air allows us to understand the types of contaminants that are present and devise management protocols to ensure workplace safety. Inhalable air samplers offer a perfect way to test the contaminants staff encounter on the job.
What are inhalable air samplers?
Inhalable air samplers capture the dust, aerosols, and particulates that a worker might be exposed to at work. In the 1980s, the Institute of Occupational Medicine (IOM) developed the first sampling heads for collecting inhalable particle fractions that are representative of what may be breathed in through the nose and mouth.
Before using any inhalable air sampler, it must be calibrated; the IOM recommends a flow rate of 2 L/min for personal respirable sampling. Once calibrated, the head of the device is clipped on to the front of clothing, in the “breathing zone,” and is attached to a personal pump for sample collection.
Types of inhalable sir samplers
The two main types of inhalable air samplers are disposable and reusable. The reusable sampler cassette can be used repeatedly but requires dismantling and cleaning between each use, while the disposable ones are designed only for one-time use, eliminating the need for cleaning altogether.
Components of inhalable air samplers
The inhalable samplers are made up of many parts, which differ based on whether it is reusable or disposable. Three components that all units have are the sampling heads, cassettes, and filters. Each cassette contains a filter and is inserted into a sampling head; a cap is placed over the cassette inlet to keep unwanted debris out, and O-rings are used to ensure the units remain leak-free.
Disposable samplers come pre-assembled with the filter sealed safely inside the cassette, which together rest on top of a cellulose pad. Both the pad and the filter capsule fit securely inside the sampling head. An O-ring allows the inlet to be snapped in place to allow the flow of air.
The components of a reusable unit are slightly different, as they are designed to be dismantled, cleaned, and reassembled more than once. Just before each use, the cassette is assembled, and the sampling head is inserted. The air sampler cassette is made of two parts — the support grid and the cassette front. When assembled, a filter is sandwiched between these two sections.
The cassettes can be preloaded and brought to the site of testing in a transport clip. The clip is designed to slide on and off, and functions as an identifying tag for the cassettes when they are sent away for testing. The reusable cassettes also feature a rubber cap that seals off the cartridge, keeping air away from the filter when it is not in active use.
Calibrating your inhalable air sampler
Although the components found in disposable and reusable inhalable air samplers may be slightly different, the process of calibration and the usage method remains the same.
To set up the device for calibration, the air sampler is connected to the adapter and an outlet port using flexible tubing. Another length of tubing is connected to the barb on the adapter, and the corresponding outlet on the calibrator. To start your calibration, simply turn on the pump and adjust the airflow until you get the desired reading on the calibrator.
Disposable inhalable air sampler
One main benefit of a disposable inhalable air sampler is that the cassettes come pre-loaded. Not only does this save you time but reduces the risk of assembly error. On top of that, there is a reduced likelihood of contamination after the sampling process is complete, as there is no need for disassembly; you simply need to put the inlet cap back into the transport position and send the unit off for testing.
Disposable samplers also weigh less than reusable models, which means that you are likely to get more sensitive results and improved accuracy. For metals testing, the entire filter capsule can be digested. This accounts for wall deposits and gives accurate exposure readings. The reusable sampler requires wiping the interior walls of the cassette to get an accurate result. However, if you take thousands of samples every year and have the expertise of proper handling and controls, a reusable sampler could prove more beneficial for your facility.
Reusable inhalable air sampler
The most significant benefit of a reusable inhalable air sampler is that it can be used repeatedly, saving you time and money. It is important to remember to wear clean gloves when handling the cassettes and to use a new pair for each unit.
However, these samplers require a bit more care and attention; for example, the cassettes typically come with a transport clip. If the clip is lost, there is no way for you to send the cassette to the lab for testing. The clips usually also have a barcode on it, and it is vital to make sure it matches the one on the cassette to avoid incorrect results.
You also need to assemble the cassettes yourself, increasing the risk of human error, when matching the cassette front to the filter or the back. Additionally, there are extra costs involved in the cleaning and if the technicians do not follow proper care instructions, it can increase the likelihood of cross-contamination.
Types of contaminants
Air usually contains three types of contaminant – vapours, gases, and particulates, but inhalable air samplers are designed to exclusively measure particulates–tiny solids or liquids that are found suspended in the air.
These can vary greatly in size; while some particulates are big enough for us to see with our naked eyes, others can only be visualised under an electron microscope. The Environmental Protection Agency (EPA) divides particulate matter into two categories by size: PM10, particles that are no bigger than 10 µm in diameter; and PM2.5, those that are 2.5 µm or less in diameter.
Particulates can also be categorised by their chemical composition and physical properties, such as differences in their source material. Inhalable air samplers detect and measure five types of particulates: mists, a collection of liquid droplets in the air; aerosols, tiny solids or liquids that are suspended in a gas; fumes, gases formed from the heating and cooling of certain solids; smoke, carbon-based particles developed because of incomplete combustion; and lastly, dust which are small particles that come from a variety of sources and become temporarily suspended in the air. Many applications can raise the levels of certain particulates in the surrounding air and, therefore, require close monitoring.
The various applications for an inhalable air sampler include:
- ISO/CEN for bioaerosols
- NIOSH Method 5700 for particulate formaldehyde
- British Method MDHS 14/4 for sampling and gravimetric analysis of respirable, inhalable and thoracic aerosols
- British Method MDHS 14/3 for inhalable dust
- British Method MDHS 25/3 for organic isocyanates
- British Method MDHS 6/3 for lead
- ACGIH definition of inhalable particulate matter
- Australian standard for inhalable particulate
At the end of the day, you should make the decision to choose the right air sampling tools to monitor air quality and occupational safety at your workplace. It is important to remember that each type of inhalable air sampler comes with its own set of benefits and downsides, but the right choice ultimately comes down to your application, environment, and preferences.