To determine the concentration of a contaminant in the air, specialized equipment is needed for this assessment. Typically, air sampling pumps and/or specialized media is put on a worker for the duration of the shift (or a representative time). This media is then sent off to a lab for analysis, and a report is generated indicating the concentration a worker is exposed to during the sampled time. Comparison is then made with the regulatory exposure limits. Other means of assessment also involve using direct reading instruments. With this, we are able to get a concentration in that moment, and it does not require the sample to be sent off to a lab for further analysis. These would be, in simplest terms, the way to truly determine contaminant concentrations.