Asbestos Contractor/Supervisor Practice Exam

For how long should negative air machines operate until final clearance is achieved?

1. 24 hours a day until clearance

2. 12 hours intermittently

3. Only during working hours

4. Until the end of each work shift

The correct answer is: 24 hours a day until clearance

Negative air machines play a crucial role in maintaining air quality and ensuring the safety of environments that have been contaminated with asbestos. These machines work by creating negative pressure in the containment area, which helps to prevent the spread of asbestos fibers to other areas. The correct practice is to operate the negative air machines continuously, 24 hours a day, until final clearance is achieved. This continuous operation ensures that airborne particles are consistently filtered out of the air, maintaining a safe environment during the abatement process. It is essential to allow ample time for the negative air machines to effectively clean the air before any clearance testing is conducted. Other options suggest intermittent operation or limiting the use of these machines to specific times, which could result in incomplete air filtration. Such practices might lead to inaccurate clearance results, leaving potentially hazardous conditions unaddressed. Thus, the continuous operation until clearance is essential for ensuring that the air quality meets safety standards.