What is the procedure for a negative pressure check?

The procedure for a negative pressure check involves covering inhalation valves to assess whether the respirator maintains a proper seal when inhaling. This check is crucial to ensure that no outside air can enter the respirator during use, which would compromise the protection it provides against airborne contaminants, such as lead dust. By sealing the inhalation valves, the user can create a negative pressure within the mask; if there are no leaks, the respirator will collapse slightly against the face, indicating a proper fit.

In contrast, the other options do not serve the purpose of confirming the effectiveness of the seal for respiratory protection. Covering exhalation valves focuses on the release of air and does not assess inhalation integrity. Visual inspections provide a general assessment but do not guarantee that the respirator is sealed properly during use. Listening for sounds during inhalation may help identify obvious issues, but it does not provide a systematic way to verify that the respirator is functioning correctly under negative pressure. Thus, the most reliable method for checking the integrity of the respirator's seal is indeed to cover the inhalation valves.