Air Contamination & Monitoring

Airborne contaminants, like surface contaminants, pose a considerable threat to the health and safety of workers who are exposed to hazardous materials. Thus, air monitoring is vital for a successful health and safety program. Measuring airborne contaminants can help in making the following decisions:

• Selecting PPE
• Delineating areas where protection is needed
• Assessing the potential health effects of exposure
• Determining the need for specific medical monitoring

There are two common ways to assess airborne contaminants - direct-reading instruments and laboratory analysis:

• Direct-reading instruments can rapidly detect flammable or explosive atmospheres, oxygen deficiencies, certain gases and vapors, and ionizing radiation. However, these instruments usually detect or measure only specific classes of chemicals. Many of the direct-reading instruments that have been designed to detect one particular substance may also detect other substances (a problem known as "interference") and, consequently, may give inaccurate results regarding the substances actually found.
• Laboratory analysis can be more effective in evaluating air quality and detecting contaminants, especially those present in very small amounts. However, this method can take longer.

Any air monitoring program must take into account several uncontrollable factors that may affect the accuracy of the monitoring results. These uncontrollable factors include the following:

• Temperature - An increase in temperature increases the vapor pressure of most chemicals.
• Wind speed - An increase in wind speed can affect vapor concentrations near a freestanding liquid surface. Dusts and particulate-bound contaminants that are stirred up by wind can also affect air monitoring accuracy.
• Rainfall - Water from rainfall can cap or plug vapor emission routes from open or closed containers, saturated soil, or lagoons, thereby reducing airborne emissions of certain substances.
• Moisture - Dusts, including finely divided hazardous solids, are highly sensitive to moisture content. This moisture content can vary significantly with respect to location and time, and can also affect the accuracy of many sampling results.
• Vapor emissions - The physical displacement of saturated vapors can produce short-term, relatively high vapor concentrations. Continuing evaporation or diffusion may produce long-term low vapor concentrations and may involve large areas.
• Work activities - Work activities often require the mechanical disturbance of contaminated materials, which may change the concentration and composition of airborne contaminants.

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