Quality Assurance During a Global Pandemic: An Evaluation of Improvised Filter Materials for Healthcare Workers.

Objective: The proliferation of improvised masks during the COVID-19 pandemic has raised questions regarding filter effectiveness and safety. We sought to compare the effectiveness of commonly used improvised filter materials against N95 industry standards.

Methods: Six different filter materials commonly used in the community were tested using both single- and multi-layer configurations with the TSI 8130 automated filter tester in accordance with National Institute for Occupational Safety and Health (NIOSH) standards for N95 respirators.

Effects of respirator ambient air cooling on thermophysiological responses and comfort sensations.

This investigation assessed the thermophysiological and subjective impacts of different respirator ambient air cooling options while wearing chemical and biological personal protective equipment in a warm environment (32.7 ± 0.4°C, 49.

Unmanned assessment of respirator carbon dioxide levels: comparison of methods of measurement.

A study was performed to determine average inhaled carbon dioxide (F(I)CO2) concentrations of multiple respirators using unmanned test methods, and to compare results among test procedures to determine whether they could be used interchangeably. Respirator experiments were performed according to the National Institute for Occupational Safety and Health (NIOSH) (NF(I)CO2), standard European (ENF(I)CO2), and a modified method of the European test (BF(I)CO2) using full-facepiece air-purifying respirators and one air-purifying escape respirator. Bland-Altman statistics for determination of limits of agreement were applied to assess agreement among the various test methods.

Inspiratory flow rates during hard work when breathing through different respirator inhalation and exhalation resistances.

There has been a long-standing debate regarding the adequacy of airflow rates used in respirator certification testing and whether these test flow rates underestimate actual values. This study investigated breath by breath inspiratory peak flow rate, minute ventilation, and instantaneous flow rates of eight young, healthy volunteers walking on a treadmill at 80-85% of maximal aerobic capacity until exhaustion while wearing an air-purifying respirator with one of eight combinations of inhalation and exhalation resistance. An analysis of variance was performed to identify differences among the eight conditions.

Performance when breathing through different respirator inhalation and exhalation resistances during hard work.

Respirator inspiratory and expiratory breathing resistances impact ventilation and performance when studied independently. However, it is less clear as to how various combinations of inhalation and exhalation resistance affect user performance. The present study investigated the performance of 11 individuals during constant load, demanding work to exhaustion while wearing respirators with eight different combinations of inhalation and exhalation resistance.

Effect of differing facial characteristics on breathing resistance inside a respirator mask.

A group of subjects with a large range of facial characteristics was asked to breathe deeply while wearing a full facepiece respirator. The facial characteristics noted were head length, head depth, bizygomatic breadth, lip length, and Menton-Sellion length. External resistances to inhalation or exhalation were varied in each of the trials.

Speech intelligibility during respirator wear: influences of respirator speech diaphragm size and background noise.

This study assessed the effect of respirator speech device size on speech intelligibility and the impact of background noise on respirator communications effectiveness. Thirty-five subjects completed modified rhyme test (MRT) speech intelligibility testing procedures with and without a respirator under background noises of 40, 60, and 80 dBA. Respirator wear conditions included the use of one unmodified and three mechanical speech diaphragms modified to reduce the surface area of the vibrating inner membrane available for sound transmission.