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Concept: Respirator


Outbreaks of emerging infectious diseases have led to guidelines recommending the routine use of N95 respirators for healthcare workers, many of whom are women of childbearing age. The respiratory effects of prolonged respirator use on pregnant women are unclear although there has been no definite evidence of harm from past use.

Concepts: Health care, Medicine, Pregnancy, Childbirth, Epidemiology, Infectious disease, The Canon of Medicine, Respirator


Proper adherence to infection control precautions, including appropriate selection and use of personal protective equipment (PPE), is of significant importance to the health and well-being of perioperative personnel. Surgical masks are intended for use as a barrier to protect the wearer’s face from large droplets and splashes of blood and other body fluids; however, surgical and high-filtration surgical laser masks do not provide enough protection to be considered respiratory PPE. Potential exposure to airborne contaminants and infectious agents, including those present in surgical smoke, necessitates the use of respiratory PPE, such as a surgical N95 particulate filtering facepiece respirator. Filtering facepiece respirators greatly reduce a wide size range of particles from entering the wearer’s breathing zone and are designed to protect the user from both droplet and airborne particles. Every health care worker who must use a respirator to control hazardous exposures in the workplace must be trained to properly use the respirator and pass a fit test before using it in the workplace.

Concepts: Health care, Medicine, Infectious disease, Personal protective equipment, Protection, Protective gear, Respirator, Masks


To evaluate the performance of vaporized hydrogen peroxide (VHP) for the bio-decontamination of the high efficiency particulate air (HEPA) filter unit.

Concepts: Oxygen, Water, Hydrogen peroxide, Humidity, Respirator, Air purifier, Vaporized hydrogen peroxide, HEPA


Respiratory protective masks are used whenever it is too costly or impractical to remove airborne contamination from the atmosphere. Respirators are used in a wide range of occupations, form the military to medicine. Respirators have been found to interfere with many physiological and psychological aspects of task performance at levels from resting to maximum exertion. Many of these limitations have been investigated in order to determine quantitatively how much performance decrement can be expected from different levels of respirator properties. The entire system, including respirator and wearer interactions, must be considered when evaluating wearer performances. This information can help respirator designers to determine trade-offs or managers to plan to compensate for reduced productivity of wearers.

Concepts: Photosynthesis, Sociology, Performance, Atmosphere, Respirator, Military, Masks, Gas mask


The ability to disinfect and reuse disposable N95 filtering facepiece respirators (FFRs) may be needed during a pandemic of an infectious respiratory disease such as influenza. Ultraviolet germicidal irradiation (UVGI) is one possible method for respirator disinfection. However, UV radiation degrades polymers, which presents the possibility that UVGI exposure could degrade the ability of a disposable respirator to protect the worker. To study this, we exposed both sides of material coupons and respirator straps from four models of N95 FFRs to UVGI doses from 120 to 950 J/cm(2). We then tested the particle penetration, flow resistance and the bursting strengths of the individual respirator coupon layers, and the breaking strength of the respirator straps. We found that UVGI exposure led to a small increase in particle penetration (up to 1.25%) and had little effect on the flow resistance. UVGI exposure had a more pronounced effect on the strengths of the respirator materials. At the higher UVGI doses, the strength of the layers of respirator material was substantially reduced (in some cases, by >90%). The changes in the strengths of the respirator materials varied considerably among the different models of respirators. UVGI had less of an effect on the respirator straps; a dose of 2360 J/cm(2) reduced the breaking strength of the straps by 20% to 51%. Our results suggest that UVGI could be used to effectively disinfect disposable respirators for reuse, but the maximum number of disinfection cycles will be limited by the respirator model and the UVGI dose required to inactivate the pathogen.

Concepts: Ultraviolet, Hydrogen peroxide, Materials science, Disinfectant, Hygiene, Sunburn, Respirator, Ultraviolet germicidal irradiation


ABSTRACT Respiratory protection provided by a particulate respirator is a function of particle penetration through filter media and through faceseal leakage. Faceseal leakage largely contributes to the penetration of particles through respirator and compromises protection. When faceseal leaks arise, filter penetration is assumed to be negligible. The contribution of filter penetration and faceseal leakage to total inward leakage (TIL) of submicron size bioaerosols is not well studied. To address this issue, TIL values for two N95 filtering facepiece respirator (FFR) models and two surgical mask (SM) models sealed to a manikin were measured at 8 L and 40 L breathing minute volumes with different artificial leak sizes. TIL values for different size (20-800 nm, electrical mobility diameter) NaCl particles representing submicron size bioaerosols were measured using a scanning mobility particle sizer. Efficiency of filtering devices was assessed by measuring the penetration against NaCl aerosol similar to the method used for NIOSH particulate filter certification. Results showed that the most penetrating particle size (MPPS) was ∼45 nm for both N95 FFR models and one of the two SM models, and ∼350 nm for the other SM model at sealed condition with no leaks as well as with different leak sizes. TIL values increased with increasing leak sizes and breathing minute volumes. Relatively, higher efficiency N95 and SM models showed lower TIL values. Filter efficiency of FFRs and SMs influenced the TIL at different flow rates and leak sizes. Overall, the data indicate that good fitting higher efficiency FFRs may offer higher protection against submicron size bioaerosols.

Concepts: Sociology, Aerosol, Respirator, Filters, Leak, Masks, Bioaerosol, Surgical mask


A novel positive-polarity electrostatic precipitator (ESP) was developed using an ionization stage (0.4 x 0.4 x 0.14 m(3) ) with 16 carbon fiber ionizers in each channel and a collection stage (0.4 x 0.4 x 0.21 m(3) ) with parallel metallic plates. The single-pass collection efficiency and clean air delivery rate (CADR) were measured by standard tests using KCl particles in 0.25-0.35 μm. Performance was determined using the Deutsch equation and established diffusion and field-charging theories, and also compared with the commercialized HEPA filter type air cleaner. Experimental results showed that the single-pass collection efficiency of the ESP ranged from 50 to 95% and decreased with the flow rate (10 to 20 m(3) /min) but increased with the voltage applied to the ionizers (6 to 8 kV) and collection plates (-5 to -7 kV). The ESP with 18 m(3) /min achieved a CADR of 12.1 m(3) /min with a voltage of 8 kV applied to the ionization stage, and with a voltage of -6 kV applied to the collection stage. The concentration of ozone in the test chamber (30.4 m(3) ), a maximum value of 5.4 ppb over 12 hours of continuous operation, was much lower than the current indoor regulation (50 ppb). © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

Concepts: Academic publishing, John Wiley & Sons, Wiley-Blackwell, Respirator, Filters, Air purifier, Air ioniser, Clean Air Delivery Rate


For pandemic influenza outbreaks, the Institute of Medicine has recommended using a surgical mask cover (SM) over N95 filtering facepiece respirators (FFRs) among healthcare workers as one strategy to avoid surface contamination of the FFR which would extend its efficacy and reduce the threat of exhausting FFR supplies. The objective of this investigation was to measure breathing air quality and breathing resistance when using FFRs with US Food and Drug Administration-cleared SM and without SM.

Concepts: Oxygen, Carbon dioxide, Influenza, Respirator, Masks


BACKGROUND: We compared three policy options for the use of medical masks and N95 respirators in healthcare workers (HCWs). Design: A cluster randomised clinical trial of 1669 hospital-based HCWs in Beijing, China in the 2009/2010 winter. METHODS: Participants were randomised to: medical masks; N95 respirators; targeted use of N95 respirators while doing high-risk procedures or barrier nursing. Outcomes included clinical respiratory illness (CRI) and laboratory-confirmed respiratory pathogens in symptomatic subjects. Findings: The rate of CRI was highest in the medical mask arm (98/572, 17%), followed by the targeted N95 arm (61/516, 11•8%), and the N95 arm (42/581, 7•2%), P < 0•05. Bacterial respiratory tract colonisation in subjects with CRI was highest in the medical mask arm (14•7%, 84/572), followed by the targeted N95 arm (10•1%, 52/516) and lowest in the N95 arm (6•2%, 36/581), P = 0•02. After adjusting for confounders, only continuous use of N95 remained significant against CRI and bacterial colonisation, and for just CRI compared to targeted N95 use. Targeted N95 use was not superior to medical masks. Interpretation: Continuous use of N95 respirators was more efficacious against CRI than intermittent use of N95, or medical masks. Most policies for HCWs recommend use of medical masks alone, or targeted N95 respirator use. Also continuous use of N95's resulted in significantly lower rates of bacterial colonisation, a novel finding which points out to more research on the clinical significance of bacterial infection in symptomatic HCWs. This study provides further data to inform occupational policy options for HCWs.

Concepts: Immune system, Health care, Bacteria, Infection, Respirator, Mask, Masks, Gas mask


NIOSH published a Federal Register Notice to explore the possibility of incorporating FDA required filtration tests for surgical masks (SMs) in the 42 CFR Part 84 respirator certification process. There have been no published studies comparing the filtration efficiency test methods used for NIOSH certification of N95 filtering facepiece respirators (N95 FFRs) with those used by the FDA for clearance of SMs. To address this issue, filtration efficiencies of “N95 FFRs” including six N95 FFR models and three surgical N95 FFR models, and three SM models were measured using the NIOSH NaCl aerosol test method, and FDA required particulate filtration efficiency (PFE) and bacterial filtration efficiency (BFE) methods, and viral filtration efficiency (VFE) method. Five samples of each model were tested using each method. Both PFE and BFE tests were done using unneutralized particles as per FDA guidance document. PFE was measured using 0.1 µm size polystyrene latex particles and BFE with ∼3.0 µm size particles containing Staphylococcus aureus bacteria. VFE was obtained using ∼3.0 µm size particles containing phiX 174 as the challenge virus and Escherichia coli as the host. Results showed that the efficiencies measured by the NIOSH NaCl method for “N95 FFRs” were from 98.15 to 99.68% compared to 99.74 to 99.99% for PFE, 99.62 to 99.9% for BFE and 99.8 to 99.9% for VFE methods. Efficiencies by the NIOSH NaCl method were significantly (p = <0.05) lower than the other methods. SMs showed lower efficiencies (54.72 to 88.40%) than "N95 FFRs" measured by the NIOSH NaCl method, while PFE, BFE and VFE methods produced no significant difference. The above results show that the NIOSH NaCl method is relatively conservative and is able to identify poorly performing filtration devices. The higher efficiencies obtained using PFE, BFE and VFE methods show that adding these supplemental particle penetration methods will not improve respirator certification.

Concepts: Bacteria, Staphylococcus aureus, Measurement, Metrology, Escherichia coli, Test method, Measuring instrument, Respirator