Do-It-Yourself (DIY) submicron- and micron- verification of 80% to 95% particle filtration efficiency (5x-20x protection factor) at nose level, facially unobstructed without masks using wearable devices, for clean air travel amidst air pollution (e.g. Delhi) and airborne infection (e.g. long flights) especially while eating/drinking

BackgroundAir 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 24x7 during the worst stagnant pollution days may reduce daily inhaled exposure to annual averages in Delhi. MethodsHandheld 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. ResultsAt 0.3 {micro}m 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 {micro}m particles at nose level. At 1.0 {micro}m and 5.0 {micro}m at nose-level, they measured 94-99% and 95-99% respectively. "Sleep" measured 91% at 0.3 {micro}m 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. ConclusionsIn 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).