When does the potential for exposure to fumigants significantly increase?

The potential for exposure to fumigants significantly increases when tarps are being perforated or removed because this is a critical point in the fumigation process where the containment of the fumigant is temporarily disrupted. When tarps are perforated or taken off, it can lead to fumigant gases escaping into the environment, thereby increasing the risk of exposure to both the workers involved and anyone nearby. This is particularly hazardous as the fumigants are highly volatile and can spread quickly, leading to harmful health effects if inhaled.

In contrast, the other scenarios listed represent conditions where exposure is more controlled or monitored. For instance, when fumigators are in training, they typically work under supervision and may have restricted exposure to fumigants. During air monitoring procedures, environmental conditions are actively assessed to ensure safety, further mitigating exposure risks. Once the job is completed, the fumigants should have dissipated, and precautions are typically in place to ensure no residual contamination remains that could cause exposure. Thus, the highest risk coincides with the manipulation of tarp materials during the fumigation process.