What does "negative air pressure" mean in an asbestos containment area?

The concept of "negative air pressure" in an asbestos containment area refers to the intentional maintenance of lower air pressure within that space compared to the pressure outside it. This is a critical safety measure designed to prevent the escape of harmful asbestos fibers into the surrounding environment.

By sustaining a negative pressure, any air that might leak from the containment area flows into, rather than out of, the area, ensuring that potentially hazardous materials remain securely contained. This is essential during asbestos removal or remediation work, as it helps protect workers and the public from exposure to airborne asbestos.

The other options do not accurately capture the essence of negative air pressure. For instance, an environment with air pressure that is equal to the outside or higher does not provide the necessary containment protections that a negative pressure system does. Additionally, complete blockage of airflow would not facilitate the necessary ventilation needed for worker safety, and it could potentially lead to a buildup of hazardous conditions within the containment area. Therefore, the correct answer is that negative air pressure means air pressure is lower than outside, safeguarding against fiber escape.