For a respirator to be effective, what is a necessary condition regarding the fit?

For a respirator to be effective, it is crucial that it fits snugly against the face. A proper fit ensures that there are no gaps between the respirator and the skin, which could allow harmful airborne particles, vapors, or gases to enter. When the respirator seals properly, it provides a protective barrier that prevents contaminants from bypassing the filter and entering the respiratory system.

The snug fit also helps maintain the correct air pressure within the respirator, which is vital for its intended function. If the mask is loose, it will not provide adequate protection, as contaminants can easily leak in through the sides. This highlights the importance of careful fitting and adjustment to the individual user's face shape during the respirator's initial use and before any hazardous task is undertaken.