What rate of air filtration (ACH) can emulate protection of an N95 respirator in an unventilated room and how can it be checked?

There is an immediate need for efficient networks to detect and control novel/emerging bioaerosol threats. In 2022, the Pentagon Force Protection Agency (PFPA) found detection of emerging bioaerosol threats to be "not feasible for daily operations" due to cost of reagents used for metagenomics, cost of sequencing instruments, and time/cost for labor (subject matter expertise) to analyze bioinformatics. If the Pentagon experiences these operational difficulties, they may also extend to many of the 280,000 buildings (2.3 billion square feet) at 5000 secure US DoD military sites, 250 US Navy ships, and beyond in civilian buildings around the world. These economic barriers can still be addressed in a threat-agnostic manner by dynamically pooling samples from a network of dry filter units (DFUs) to detect spatio-temporally correlated "spikes" in novel pathogen concentrations, termed Spike Triggered Virtualization (STV). In STV, pooling and sequencing depth are automatically modulated in the next cycle in response to novel potential biothreats in the sequencing output of the previous sequencing cycle. By running at a high pooling factor and lower depth unless triggered by a potential pathogen spike, average daily and annual cost per DFU can be reduced by one to two orders of magnitude depending on chosen trigger thresholds. Artificial intelligence (AI) can further enhance sensitivity of STV triggers. Risk of infection remains during the 12-24 hour window between a bioaerosol incident and its detection, but can in some cases be reduced by 80% or potentially more with high-speed indoor air cleaning exceeding 10 air changes per hour (10 ACH) similar to passenger airplanes (Airbus A319, A321 and a Boeing 737-Max8/9) that were tested in flight. Costs of 4 ACH or higher are expected to rise non-linearly with ACH using central HVAC systems and be cost-prohibitive. Whereas 10 ACH or more can be achieved economically by recycling the air in rooms with low-noise, portable air filtration systems tested herein for which costs scale linearly with ACH. For typical ceiling heights (< 10 ), the cost per square foot cost for low-noise air filtration exceeding 10 ACH was found to be approximately $0.5 to $1 for Do-It-Yourself (DIY) and $2 to $5 for HEPA.