Breakthrough analysis for filtering facepiece respirators impregnated with activated carbon

Several manufacturers are producing disposable dual-use dust masks that are primarily designed to protect against airborne particulate exposures but that also contain a layer of activated carbon to provide protection against organic vapors (OVs) at levels below permissible exposure levels, referred to as "nuisance level" by the FFR manufacturers. Industries identified in the literature as commonly having employees exposed to nuisance-level OVs include beautician salons, dry cleaning operations, and pesticide applications. This study investigated the adsorption capabilities of three different dual-use dust masks that contain both filter media to remove particles and activated carbon to capture OVs. The three dual-use dust masks were tested and compared relative to the 50% breakthrough time for two OVs (acetone and perchloroethylene) and one non-carbon-based contaminant gas (ammonia) often found in agricultural settings at nuisance-level amounts. The dual-use dust masks were exposed to 15 ppm and 50 ppm for all 3 compounds, which represented the range of nuisance-level exposure documented in literature. Most tests were conducted at 21 °C and 50% relative humidity. A relative humidity level of 95% was also created to compare results under that condition. The non-approved dual-use dust masks were ineffective for all vapors and offered less than 10 min of protection before 50% breakthrough occurred. All dual-use dust masks performed poorly when exposed to ammonia, with breakthrough time less than 7 min at 50 ppm and 10 min at 15 ppm. The approved dual-use dust mask had 50% breakthrough times, for example, of 121 min and 233 min for acetone at 15 ppm and 50 ppm, respectively. The less volatile perchloroethylene took over 400 min to achieve 50% breakthrough at 50 ppm. High relative humidity reduced breakthrough times by up to 70%. These results indicate high variability in performance among dual-use dust masks. Performance is also dependent on gas/vapor volatility and levels of water vapor. However, one model tested, the 3M model 8514, did show promise as an acceptable method for greatly reducing nuisance-level OV exposures.

Controlling Transmission of MRSA to Humans During Short-Term Visits to Swine Farms Using Dust Masks

The aim of the investigation was to determine the protective effect of wearing dust masks to prevent Methicillin-resistant Staphylococcus aureus (MRSA) contamination during a short-term visit in a MRSA-positive swine farm. A total of 118 human volunteers were randomly allocated to a group wearing masks and to the control group. On average, 9% of the participants wearing masks were MRSA-positive when leaving the farm compared to 62% of the participants not wearing masks. At day 1, 2, and 7 after the farm visit, none of those wearing masks were MRSA-positive. An odds ratio of 18.9 (CI: 6.4-56.2) for being MRSA-positive was found for those not wearing masks compared to those wearing masks when including the farm as random effect. None of the covariates (gender, age, and smoking) influenced the OR for being MRSA-positive when leaving the farm. This study shows that the use of dust masks gives a significant protection against nasal MRSA contamination after a short-term visit to a swine farm. In addition, 106 volunteers not wearing masks were investigated in order to provide an estimate of a contamination dose of airborne MRSA. Due to the high variation in the MRSA measurements, it was not possible to establish a stable estimate for this. Out of the 106 volunteers not wearing masks, 6, 7, and 3% tested MRSA-positive 1, 2, and 7 days after the farm visit, respectively.