In industrial hygiene, there are few tests more common than for dust and particulate matter. Some dusts, which may also be referred to as aerosols, are specifically regulated, such as silica, asbestos, heavy metals, and combustible dusts. However, for most industries, general dust testing is performed. OSHA deems these “particles not otherwise regulated”, or PNOR and the ACGIH calls these “particles not otherwise specified (PNOS). These are particles that are not a part of any other regulated material and can be sampled without needing to be identified specifically.
Respirable vs Total Dust
In general dust monitoring, there are two main classifications: respirable dust and total dust. Respirable dust is the size fraction that is able to get into the gas exchange region of your lungs, where total dust is not size-selective. Respirable dust testing is a type of size-selective sampling, meaning a special sampling device is used to only collect particles of a certain size. Traditionally respirable dust testing is done using a cyclone, a special kind of sampler that is used to collect dust with a 50% cut point of 4μm. Some cyclones are aluminum and others are nylon, while in some cases IH’s will use a special sampling cassette such as a parallel particle impactor. The industry being monitored can have an effect on what kind of sampler is used. For example, nylon cyclones are typically used in underground mines where the metal cyclone could be a spark hazard. The particle size has been selected to match the size of particles that can deposit into the gas exchange region of your lungs.
Total dust testing is not size-selective, meaning that all particles regardless of size can be measured on a sample. Total dust sampling is not well defined– different samplers have different efficiencies at collecting various sized particles. Total dust sampling is usually performed using a 37mm cassette with a low volume pump. The filter in the cassette is weighted on a precise scale prior to sampling, and then weighted again after sampling to determine the amount of dust present.
Performing Dust Testing
Dust monitoring is typically done for the duration of the work shift for representative employees. Different job responsibilities have different exposure potentials, so typically multiple employees are monitored. For example, if one employee sands wood products for 8hrs and another uses a table saw for 8hrs, you would want to assess each employee separately for their exposures. Sampling should be of a representative shift, but worst-case situations should also be considered. Knowing the amount of particulate matter exposure workers deal with on a shift can inform management if potential controls should be put in place to protect workers. For example, if the employee who is sanding for a whole shift is exposed to elevated respirable dust levels, management can put engineering controls in place such as a dust shroud around the sander. Or maybe put administrative controls in place to rotate activities during the workday to prevent any one worker performing more than a specific amount of hours sanding over an 8hr shift. While particle levels can potentially be elevated in any industry, some examples of typical industries that have particulate matter concerns are demolition, carpentry, and mining.
If your business is looking to perform dust monitoring or if you have other industrial hygiene needs, contact us. For most projects we can give you a quote without a site visit.