Clean Air Travel: Evaluation of Mask-Free Alternatives to N95 During the Delhi “Air Emergency”

Background Air travelers, healthcare workers aiming to prevent infection and pollution-sufferers (e.g. Delhi “Air Emergency”) may experience difficulty during prolonged use of respirators (e.g. N95) incompatible with eating/drinking/sleeping. Protection factor of 5x-1000x (80%-99.9%) is targeted for infection prevention. Daily PM 2.5 time-series data suggest at least 4x-5x (75%-80%) protection factor 24×7 during the worst stagnant pollution days may reduce daily inhaled exposure to annual averages in Delhi. Methods Handheld Do-It-Yourself test methods were developed using a 7-channel optical particle counter. Three baseball cap visor-mounted air purifiers were prototyped enabling eating/drinking, “Air” (1 lb), “Pro” (2 lb), “Max” (2 lb 10 oz), and one bed-mounted prototype, “Sleep”. Clean air delivery rate per watt was measured for vertically stackable portable air purifiers to optimize power/floorspace/cost-efficiency. Results At 0.3 µm at nose-level, “Air” measured 87%, “Pro” measured 94%, “Max” measured 98%, a 2x-10x improvement in particle penetration over prior wearable purifiers (unobstructed in horizontal and lower visual fields) reporting approximately 60% (< 70%) of 0.3 µm particles at nose level. At 1.0 µm and 5.0 µm at nose-level, they measured 94–99% and 95–99% respectively. “Sleep” measured 91% at 0.3 µm at nose level. Stackable air purifiers measured 6-19 ACH in ∼3000 cubic foot room (300-900 cubic feet per minute) at 20-220 watts, with highest power-efficiency 19 CFM/Watt at 962 CFM. Conclusions In principle, maskless alternatives to N95 combine with floorspace- and power-efficient stackable/sleeping air purifiers for protection factor of 99%-99.98% (100x-5000x) in airplanes, submarines, ships, trains, hospitals, shelters with limited floorspace (e.g. berths).