Verify the Boundaries of the Hazard Zone. This is the primary mission of the air sampling professional at an accidental release of hazardous materials. Remember that air monitoring is the primary tool that determines the hazard zones around a release of hazardous materials. Interpret the Air Monitoring results with knowledge of weather. The air sampling professional needs to use information about the existing and predicted weather in interpreting the results.
Weather is fickle.
Wind speed, wind direction, atmospheric stability are all subject to variations which can cause air concentration gradients to change rapidly. Record weather conditions and frequently update predictions of weather every time air sampling results are evaluated in the determination of the hazard zone boundaries. The concentrations of hazardous constituents in the air are subject to change, depending upon how the substance is directly released to the atmosphere and how the weather is changing. The air sampling professional needs to determine how frequently the grid is to be resampled, based upon site specific conditions. For example, a volatile release from a pool of liquid that is not increasing or decreasing in size in a relatively constant weather condition does not need to be sampled as frequently as a situation involving a gaseous release from a broken valve or pipe on a day when there is a wind shift predicted.