Respiratory Protection I

Podium Session 117

Tuesday, June 3, 2014, 2:00 PM - 4:30 PM 

SR-117-01 Protection offered by an Improperly Sized, Loose-Fitting Powered Air-Purifying Respirator Against Sub-Micrometer Aerosol Particles 

S. Gao, University of Cincinnati, Cincinnati, OH; M. Yermakov, University of Cincinnati, Cincinnati, OH; J. Kim, University of Cincinnati, Cincinnati, OH; R. McKay, University of Cincinnati, Cincinnati, OH; T. Reponen, University of Cincinnati, Cincinnati, OH; S. Grinshpun, University of Cincinnati, Cincinnati, OH 

Objective: To quantify the protection offered by an improperly sized, loose-fitting powered air-purifying respirator (PAPR). 

Methods: Two different loose-fitting facepieces attached to a PAPR operating at a flow rate of 198 L/min were challenged with the NaCl aerosol while donned on a small manikin headform in the exposure chamber. The tests were conducted at 25 constant inhalation flows ranging from 0 to 250 L/min and four cyclic flows with mean inspiration flow (MIF) rates of 30, 55, 85 and 135 L/min. Each experiment was performed with sealed and unsealed exhaust holes. The total particle concentration inside (Cin) and outside (Cout) of the facepiece was measured using a condensation particle counter operating in the size range of 20-1000 nm. The protection factor was determined as Cout/Cin. Additionally, the air flow dynamics was studied using the flow visualization technique. 

Results: The measured protection factor varied approximately from 3.5 to 60,680 and was above the assigned protection factor (APF) of 25 at an inhalation flow of about 120160 L/min. Under the constant flow regime, the protection factor decreased exponentially as the inhalation flow rate increased from 0 to about 140 L/min. This exponential trend slowed down once the inhalation flow rate exceeded about 150 L/min and almost diminished as it surpassed the one generated by the blower (198 L/min). The measured values are consistent with visual observations made with an airflow indicator. The gap size between the facepiece and face as well as the total surface area of exhaust holes were found to be important factors affecting the respirator performance. As expected, increase in the gap area caused a decrease of the protection factor. Under the cyclic flow regime, the protection factor also decreased exponentially with MIF and exceeded the APF=25 for all tested MIFs. 

Conclusions: The results suggest that gap size and breathing flow rate affect the level of protection offered by PAPRs. This information is important for program administrators and others responsible for sizing loose-fitting facepieces to respirator wearers. 


SR-117-02 Evaluation of the NIOSH Proposed STP for Fit Testing Half Facepiece Respirators 

C. Colton, 3M Personal Safety Division, St. Paul, MN; P. Eitzman, 3M Personal Safety Division, St. Paul, MN; R. Hehenberger, 3M Safety and Graphics Business, Shanghai, China; M. Luinenburg, 3M Personal Safety Division, St. Paul, MN 

Objective: The National Institute for Occupational Safety and Health (NIOSH) proposed changing the certification requirements for half mask air-purifying respirators by adding new fit test requirements. The proposed requirements [74 Federal Register 56141] and standard test procedure (STP) were never evaluated to determine if NIOSH’s STP and the proposed acceptance criteria were capable of eliminating poor-fitting respirators from the workplace without eliminating well-fitting respirators. 

Methods: In this study, the proposed requirements and STP were followed in evaluating several well-fitting and one poor-fitting respirator to determine the test’s capability to distinguish between them and if not, what criteria would be appropriate for such a test procedure. 

Results: The results of this study indicate that the proposed STP and the acceptance criteria cannot distinguish between well- and poor-fitting respirators without eliminating well-fitting respirators. As proposed, these new requirements would eliminate at least 40 percent of the well-fitting respirators from the market. 

Conclusions: Further analysis indicates that the NIOSH proposal needs to be modified to achieve its purpose by either increasing the bivariate test panel size to 105 subjects using the proposed subject face size distribution or changing the pass/fail criteria. These test results indicate, as an alternative, that changing the passing fit factor to 50 for 18 out of 35 panel subjects and removing the “one pass per cell” requirement will provide good discrimination between well- and poor-fitting filtering facepiece respirators. 


SR-117-03 Respiratory Protection for Firefighters- Evaluation of CBRN Canisters During Overhaul 

L. Jones, University of Arizona, Tucson, AZ; E. Lutz, University of Arizona, Tucson, AZ 

Objective: This study assesses the filtering performance of 3 brands of commercially available CBRN canisters and 1 cartridge. The authors hypothesize when in actual overhaul environments following suppression of live-fire burns of structural and residential materials, that each CBRN canister provides adequate respiratory protection, when challenged at overhaul-relevant exposure times and at a realistic flow rate. 

Methods: Three different CBRN canisters and one CBRN cartridge were challenged in repetitive exposure tests using a sampling manifold apparatus of our own design. Twelve tests were conducted at ~80L/min at 3 different time periods (0-15min, 0-30min and 0-60min). Similar quantities of common household items were used during the burns to simulate actual overhaul environments. In each test cycle, fires were allowed to burn for 10 minutes before they were suppressed with water per standard firefighter procedures. A Kruskal-Wallis test was performed to determine any significance of measured contaminants between each CBRN canister and also between each time period. A Wilcoxon Rank Sum test with Bonferroni adjustment was performed to determine if there was any significance within the groups. For all tests, an alpha of 0.05 (95 percent CI) was used. 

Results: Fourteen of the 21 measured contaminant concentrations above LOG were also detected downstream of a CBRN canister/cartridge. Of the contaminants measure above the LOQ, formaldehyde and respirable particulates were the only contaminants the measured above ACGIH ceiling limits. Results of the statistical analysis confirm that for formaldehyde, all CBRN canisters/cartridges concentrations were significantly reduced (p= 0.0063) independent of time and dependent of time all CBRN canisters/cartridges concentrations of formaldehyde showed no statistical significance. Results also show that for concentration of personal aerosols, all CBRN canisters were significant in reducing concentrations (p= 0.0008). 

Conclusions: The commercially available CBRN canisters/cartridges evaluated in this study were each effective in reducing concentrations of hazardous chemicals and respirable particulates. Based on these findings, the CBRN canisters tested are recommended for use during overhaul operations where more effective respiratory protection is not used or unavailable (such as self-contained breathing apparatus). 


SR-117-05 Effectiveness of Exhalation Valves on N95 Filtering Facepiece Respirator Performance 

A. Sabolis, Scott Safety, Monroe, NC; D. Symons, Scott Safety, Monroe, NC; J. Maness, Scott Safety, Monroe, NC; W. Milbrandt, Scott Safety, Monroe, NC; M. Parham, Scott Safety, Monroe, NC 

Objective: Recent literature has shown that several parameters affect the comfort/tolerability of prolonged N95 Filtering Facepiece Respirator (FRR) usage. Some of these parameters include: breathing resistance, skin irritation, dead space heat, dead space moisture, and high inhaled carbon dioxide. The objective of this study was to determine the significance of exhalation valves on N95 FRRs, with respect to Work of Breathing (WOB), dead space heat burden, and CO2 content, by comparing currently available N95 FRRs with and without exhalation valves. 

Methods: A total of 10 N95 FRRs were tested, 5 unique masks both with and without exhalation valves. Three different testing methods were used to evaluate performance of the N95 masks. Work of Breathing (WOB) is the work required by the respiratory system to overcome added resistances (from FRRs) while breathing. For the WOB test method, masks were mounted on a bellows type breathing machine where mask pressure and tidal volume were measured simultaneously and WOB was calculated. This same test setup was used for dead space heat burden, but with heated air added to the system and temperature measurements taken inside and outside the mask. Inhaled carbon dioxide content was also quantified. 

Results: It was found that N95 masks with exhalation valves performed better than their non-exhalation valve companion in all three parameters. But for WOB and dead space heat burden, there was more variation in performance when comparing the unique mask types, than comparing the same mask with and without exhalation valves. This holds true at both low and high breathing rates. However, when compared against other masks types, masks that contained exhalation valves always had lower CO2 content than non exhalation valve masks. CO2 content in the mask dead space was reduced, on average, 25 percent with the inclusion of an exhalation valve. 

Conclusions: Our results suggest that exhalation valves on N95 FRRs appear to have the greatest impact on reducing CO2 in the mask. The variation in N95 mask design and filtration media selection has a higher impact on performance with respect to WOB and heat burden, than the inclusion of an exhalation valve. Novel valve designs may be necessary to help reduce WOB and heat burden in N95 masks to improve user comfort/tolerability.