Which type of pressure check involves sealing the respirator and inhaling?

The type of pressure check that involves sealing the respirator and inhaling is known as a negative pressure check. During this procedure, the user places their hands over the respirator's filters or inhalation valves and inhales sharply; if the respirator is effectively sealed, it will collapse slightly against the user's face, indicating that there is a proper fit. This method is essential for ensuring that no outside air can enter through gaps, which is critical for the respirator to provide the necessary protection from hazardous airborne contaminants.

In contrast, a positive pressure check would involve sealing the exhalation valve and exhaling gently to create a slight positive pressure inside the mask. If the mask remains inflated and no air escapes, it is also well sealed, but this is not the method being described in the question. Similarly, while both positive and negative pressure checks are part of determining the effectiveness of a respirator's fit, the specific action described in the question aligns solely with the negative pressure check. Quantitative pressure checks refer to processes that involve measuring the actual amount of leakage and employ specialized equipment, making them different from the straightforward inhalation method highlighted here.