Effects of Breathing Frequency and Flow Rate on the Total Inward Leakage of an Elastomeric Half-Mask Donned on an Advanced Manikin Headform

Abstract

Objectives The objective of this study was to investigate the effects of breathing frequency and flow rate on the total inward leakage (TIL) of an elastomeric half-mask donned on an advanced manikin headform and challenged with combustion aerosols. Methods An elastomeric half-mask respirator equipped with P100 filters was donned on an advanced manikin headform covered with life-like soft skin and challenged with aerosols originated by burning three materials: wood, paper, and plastic (polyethylene). TIL was determined as the ratio of aerosol concentrations inside (Cin) and outside (Cout) of the respirator (Cin/Cout) measured with a nanoparticle spectrometer operating in the particle size range of 20–200 nm. The testing was performed under three cyclic breathing flows [mean inspiratory flow (MIF) of 30, 55, and 85 l/min] and five breathing frequencies (10, 15, 20, 25, and 30 breaths/min). A completely randomized factorial study design was chosen with four replicates for each combination of breathing flow rate and frequency. Results Particle size, MIF, and combustion material had significant (P < 0.001) effects on TIL regardless of breathing frequency. Increasing breathing flow decreased TIL. Testing with plastic aerosol produced higher mean TIL values than wood and paper aerosols. The effect of the breathing frequency was complex. When analyzed using all combustion aerosols and MIFs (pooled data), breathing frequency did not significantly (P = 0.08) affect TIL. However, once the data were stratified according to combustion aerosol and MIF, the effect of breathing frequency became significant (P < 0.05) for all MIFs challenged with wood and paper combustion aerosols, and for MIF = 30 l/min only when challenged with plastic combustion aerosol. Conclusions The effect of breathing frequency on TIL is less significant than the effects of combustion aerosol and breathing flow rate for the tested elastomeric half-mask respirator. The greatest TIL occurred when challenged with plastic aerosol at 30 l/min and at a breathing frequency of 30 breaths/min.

Penetration of Combustion Aerosol Particles Through Filters of NIOSH-Certified Filtering Facepiece Respirators (FFRs)

“…This finding is consistent with our previous studies, which were conducted using elastomeric half-mask with P100 filters. (6,18)…”

“…Three types of combustion particles, including wood, paper and plastic, were generated in a test chamber by burning a wood stick (24 cm long and 0.4 cm diameter, 1.9 ± 0.5 g), a sheet of paper (23 × 24 cm brown multifold paper towel, 2.1 ± 0.2 g), and a plastic straw (19 cm long and 0.5 cm diameter, 0.6 ± 0.01 g), respectively, using the protocol described elsewhere. (6) The burning materials were held by a caliper with a water-filled basin right under it, and were ignited by a lighter. The measurement was started 15 min (= time zero) after the complete burning of each material to allow the particles to reach a uniform concentration inside the test chamber.…”

“…Combustion process can generate a large amount of particles and gases that are known or anticipated to be harmful to both the environment and the health. (4) Of particular importance is the combustion of ultrafine/nano-scale particles (<100 nm in size), (5,6) which can penetrate deep into the lung; once deposited, some of these particles may cross the air-blood barrier and accumulate in other organs. (7) Workers exposed to the combustion particles may be at risk for developing respiratory and cardiovascular problems.…”

Performance of N95 FFRs Against Combustion and NaCl Aerosols in Dry and Moderately Humid Air: Manikin-based Study

“…The plastic straw was ignited by a lighter and left for burning until completely consumed. The sampling devices were started to collect data 15 min after the completion of the plastic burning, which allowed the plastic particles to reach a spatial uniformity (He et al , 2014a). We were specifically interested in testing the plastic particles as our previous study showed that they penetrated through the N95 FFR filters more readily than the other two types of combustion particles (wood and paper) (Gao et al , 2015).…”

A pilot study of minimum operational flow for loose-fitting powered air-purifying respirators used in healthcare cleaning services

“…[9] In addition, annual fit-testing is required for N95 FFRs since face seal leakage would significantly affect the achieved protection. [10,11]…”