What is one characteristic that disqualifies someone from using a negative pressure respirator?

A negative pressure respirator relies on a proper seal between the respirator and the user's face to effectively filter out harmful particles, including asbestos fibers. One key factor that can compromise this sealing ability is facial hair. A beard or facial scar can prevent a tight fit, allowing contaminants to bypass the respirator and enter the breathing space. This is critical in environments where asbestos is present, as any breakthrough can lead to inhalation of dangerous particles.

In contrast, having long hair, experiencing allergies, or wearing glasses does not fundamentally affect the ability of the respirator to maintain a proper seal. Long hair can be managed with a hairnet or tied back, and while allergies may affect comfort, they do not impair the functionality of the respirator. Glasses can sometimes create a slight pressure point but can generally be accommodated without compromising the seal. Therefore, the presence of a beard or facial scar is a significant biometric consideration that disqualifies someone from effectively using a negative pressure respirator.