A pressure indicator for positive pressure protection masks, including powered air purifying respirators (PAPRs) that monitors and determines relative air pressure between the internal space of a protection mask and the ambient environment to alert users of negative or threshold level air pressure, and in turn, to ensure safe operation of the protection masks. The pressure indicator, which is incorporated in the mask, alerts users when the air pressure in the mask reaches a critical level by transmitting optical signals, auditory signals, vibrational signals or a combination thereof that are detectable by the user. The optical signals are projected into the user's line of vision either directly or through a head-up display. The pressure indicator may cause the signal to indicate a safe and danger mode, or may cause the signal to indicate only during a danger mode.