Preliminary Development of a Real-Time Respirator Seal Integrity Monitor With Low-Cost Particle Sensor

Abstract

In many industrial environments, properly fit and functioning respirators are required to reduce individual's exposure to particulate matter. Respirator fits are evaluated prior to use by the Occupational Health and Safety (OSHA) fit testing protocol. However, this testing cannot ensure that the seal is maintained during actual use. The OSHA fit testing equipment and laboratory grade aerosol monitors are both too expensive and bulky to be deployed in workplace environments. In this effort, a low cost portable device, the respirator seal integrity monitor (ReSIM) was developed to monitor the aerosol particle concentrations inside a wearer's respirator mask, alerting the wearer when seal breaches allow aerosol particles to enter the mask. Multiple low-cost particle sensors were tested, with the Shinyei PPD60PV-T2 sensor being selected. The PPD60PV-T2 sensor can detect particles of 0.5 μm and above. These large particles cannot penetrate a properly fit respirator in quantity; thus, their detection points to a compromised seal. ReSIM utilizes an air pump to consistently draw in-mask air into the sensor without allowing external air to be pulled into the mask. ReSIM aggregates all particle detection events over 30-s intervals and determines the percentage of time during, which particles are detected, identifying spikes in particle detection corresponding to seal failures. The newly-developed ReSIM system was tested with polystyrene latex spheres, salt, and combustion aerosols under different flow conditions including cyclic breathing at 30 and 85 L/min. Results obtained while testing under cyclic breathing conditions showed 96.9% accuracy in identifying intervals with leaks versus intervals without leaks.