When should a positive and negative pressure check be performed when using a half mask respirator?

A positive and negative pressure check should be performed each time the respirator is put on to ensure its proper fit and functionality. This procedure is essential for verifying that the respirator forms a secure seal around the wearer’s face, which is critical for optimal respiratory protection.

Performing this check before use allows the wearer to detect any issues such as improper sealing, which could allow contaminants to enter the respirator. The positive pressure check involves exhaling gently while wearing the mask; if the mask inflates slightly, it indicates a proper seal. Conversely, during the negative pressure check, one inhales; if the respirator collapses slightly, it shows an adequate seal.

Conducting this check each time ensures the user is protected right from the start of their work, reducing the risk of inhalation of hazardous airborne substances. While performing checks at the end of a work shift, during maintenance, or when training new users is beneficial, it does not replace the need for this crucial check before each use.