Friday, September 20, 2013

Survivability Analysis of INFLUENZA vs Portable UVC Air Purifiers and Home HEPA Air Filters

COI Statement:  We have no conflicts of interest, and make no money from any of these products
Non-commercial use only


We sought to identify if there were any home portable UVC air sterilizers on the market which might provide significant risk mitigation capability in the event of an H7N9 Influenza Pandemic. Based on design characteristics, only three home portable UVC purifiers were suitable candidates for an Influenza survivability analysis. Of those three, we eliminated one because it was advertised as also having a UVV capability to oxidize airborne chemicals.

Based on our survivability analysis, we have high confidence in only one unit:  the Swordfish portable home UVC air purifier  (#UVA1800RM).  Our results indicate that it has a one pass Probability of Kill (PK) capability against Influenza viruses which is significantly greater than the one pass Probability of Filtering (PF) capability of home portable HEPA filters of similar air flow.


We used data from the following three public research papers to derive PK and challenge values for the survivability analysis:

Aerosol Susceptibility of Influenza Virus to UV-C Light

Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks


Our methodology was based on taking published UVC lamp data, listed air flow rates, and estimated chamber sizes  to calculate minimal UVC fluence rates and air dwell time for the two units which we identified as likely having a germicidal capability against airborne Influenza.

One key design feature identifying potentially effective home portable airborne germicidal UVC units is a UVC lamp orientation axially placed in the direction of airflow (see picture below). The design parameters of HEPA filters typically preclude such an orientation, making combination home  HEPA / UVC units of dubious value.


UNIT 1:  Swordfish Model #UVA1800RM @ 30 Cubic Feet per Minute (setting 2)

PK@ 25% Relative Humidity = 0.99999999595  and  after 9000hrs = 0.999999926
PK@ 75% Relative Humidity = 0.99999956992  and  after 9000hrs = 0.999996123

A medical grade HEPA system would require three passes through its filter to remove the same quantity of Influenza as our analysis indicates the Swordfish model kills in one pass. (see chart below)

UNIT 2:  Germ Guardian Model# EV9102  @ 23 Cubic Feet per Minute

PK@ 25% Relative Humidity = 0.986  and  after 9000hrs = 0.967
PK@ 75% Relative Humidity = 0.961  and  after 9000hrs = 0.925

Our analysis indicates that the Germ Guardian would have to make five passes before it would kill the the same quantity of virus as the Swordfish. We suspect that its Influenza killing capability may be on par with the filtering capability which might be expected from a home grade HEPA unit. (see chart below)


Ideally exhausting virus laden air to the outdoors is preferable to sanitizing, filtering and recirculating stagnant room air.  But when that is not possible, our analysis indicates that against Influenza the Swordfish  Model #UVA1800RM can offer a quiet, low airflow, level of protection roughly equivalent to a louder portable medical grade HEPA unit with three times the air flow rate. We expect that value to be even higher vs a home grade HEPA unit.  Still, we envision that the Swordfish is best utilized in conjunction with HEPA units selected for significantly higher airflow rates, or in standalone mode where space / noise concerns would prevent a HEPA unit from being well utilized.

Watch the video for further detail and insight. (coming soon)


  1. Good stuff, but HEPA air filters are better for capturing radioactive particles, so both would be good.

    1. Yes, I figure most people who peruse this site all ready have HEPA filters for that purpose. Adding a good UVC unit just increases capabilities against biological threats, but does nothing for radioactive particles.