Summary
A proof-of-concept field study of ultrafine aqueous hypochlorous acid — droplets under two microns, applied as a “dry vapor” fog rather than a wet spray — across four occupied outpatient medical facilities.
Why a dry fog rather than a mist
Hypochlorous acid has been used for air purification since the 1918 influenza pandemic, but large-scale application has been held back by the equipment rather than the chemistry. Conventional aerosol droplets are over 20 microns, heavy enough to fall out and wet the room. That causes corrosion, creates slip hazards and makes the method unsafe around sensitive medical electronics, and the resulting “mist” application is labour-intensive. Droplets under two microns stay suspended, which is what this study set out to test at building scale.
How it was done
| Setting | Four outpatient facilities in daily use — an urgent care centre, an orthopedic centre, an endoscopy centre and an ophthalmology surgical centre — ranging from 4,500 to 90,000 square feet |
|---|---|
| Product used | A commercially supplied hypochlorous acid solution (Annihilyte, EPA Reg. No. 92449-1) dispersed by a Nebula One ultra dry-mist nebulizer. Neither is an EcoloxTech product. |
| Application | One operator, one device, no PPE and no modification to the heating, ventilation or air conditioning equipment. Fill times ran from 12 minutes for the smallest site to 90 minutes for the 90,000 square foot building, about one million cubic feet. |
| Measurement | ATP bioluminescence, in relative light units, from 10 × 10 cm swabs of staff, procedure and public areas — door handles, desks, keyboards, kiosks, phones and medical equipment. Samples were taken near the end of the workday, before customary cleaning, with sites tagged so the same surface was re-swabbed each time. |
| Design | 141 sample sites across the four facilities, measured at baseline, 30 minutes and 60 minutes. A control series with no HOCl application was run at one site on a separate day following the same protocol. |
Result
| Site | Baseline (mean RLU) | 30 min | 60 min | n |
|---|---|---|---|---|
| 1 | 138.02 | 38.02 | 16.95 | 62 |
| 2 | 243.47 | 176.93 | 76.80 | 30 |
| 3 | 153.60 | 43.32 | 25.80 | 25 |
| 4 | 127.88 | 36.75 | 19.75 | 24 |
| All sites | 161.49 | 68.13 | 31.73 | 141 |
Reductions at both 30 and 60 minutes were statistically significant against baseline (Wilcoxon signed rank, p < 0.001), as was the further fall between 30 and 60 minutes. A Kruskal-Wallis test found no significant difference in the size of the reduction between facilities, so the effect did not depend on building size. Control samples showed no significant change at either time point.
The authors report every facility finishing below the ATP levels commonly treated as “disinfected” for terminal cleaning of non-surgical hospital areas, and often below the stricter figure associated with operating-room standards.
What this establishes, and what it does not
- ATP is a proxy, not an organism count. ATP bioluminescence measures organic residue. It is among the options the CDC lists for monitoring environmental cleaning, but it is not standardised between systems and it neither identifies nor enumerates any pathogen. The authors say so directly and call for culture-based assays in further work.
- It is an acute measurement. Sampling stopped at 60 minutes. Nothing here speaks to how long the effect lasts, how often application would need repeating, or to airborne efficacy, all of which the authors list as open questions.
- Manual cleaning was not replaced. The paper notes that manual cleaning remains an EPA regulatory requirement prior to disinfection.
- Declared interests. The equipment manufacturer assisted with study design and data acquisition; the lead author serves as its chief medical officer, and three authors were employed by the clinical group whose facilities were used. The paper discloses this, and it is worth weighing when reading the result.
- It is not an EcoloxTech study and it is not a product claim. EcoloxTech generators are regulated by the EPA as devices and carry no efficacy claims. Our registered product, HOCl-AS200 (EPA Reg. No. 101112-1), may be used only according to its accepted label, which does not include fogging.
What it means in practice
Ultrafine fogging covered a 90,000 square foot facility in 90 minutes with one operator and no protective equipment, and left surface ATP below the levels commonly used as a terminal-cleaning threshold. Because ATP measures organic residue rather than organisms, this is evidence about disinfection logistics at building scale, not about any particular pathogen.
Conditions tested
| Parameter | Value |
|---|---|
| Concentration | 500 ppm solution, nebulised to under 300 micrograms per cubic metre in air |
| Contact time | 30 and 60 minutes after application |
| Measured result | Mean surface ATP fell from 161 RLU to 68 RLU at 30 minutes and 32 RLU at 60 minutes across 141 sample sites |
| Organisms | Total microbial count |
| Relevant sectors | Contact surfaces, Healthcare, Public health |
| Publication | Frontiers in Cellular and Infection Microbiology, 2026 |
| Authors | Reed B. Hogan II, Eleni Mijalis, Charlotte Green, Terrell Porter, Christopher Spankovich |
Reading this responsibly
Published figures are obtained under controlled conditions, usually on clean surfaces or in defined matrices. Organic load, surface condition, temperature and application coverage all affect real-world performance. Use these numbers to design a protocol, then validate it on your own site with environmental swabbing.
Applying it
Concentrations in this range are within the adjustable output of every EcoloxTech commercial system, so implementing this protocol is a settings question rather than a procurement one. Where the claim needs to sit on a registered label, see HOCl-AS200, EPA Reg. No. 101112-1.