What is the evidence of efficacy for the hypochlorous acid fogger for disinfection?  

Posted on June 4, 2020 by Madalon Burnett


The efficacy for hypochlorous acid foggers against COVID-19 has not been evaluated. Hypochlorous acid foggers are effective against norovirus and against fungi/bacteria in daycares. The WHO recommends against any fog or spray based disinfection for uses related to the COVID-19 pandemic.

I.   Guidelines

The WHO states “routine application of disinfectants to environmental surfaces by spraying or fogging (also known as fumigation or misting) is not recommended for COVID-19” (1).

II.   Background


  • Hypochlorous acid (HOCl) is the active ingredient in bleach (2). Bleach is known to inactivate a wide variety of viruses, including coronavirus 229E (3). Bleach is the current recommended cleaning agent for surfaces by the government of Canada (4).

  • Manufacturers of HOCl foggers claim that their products efficiently inactivate viruses, bacteria, and fungi. They also claim that their products are safe to use without PPE. The authors of these claims call their product “electrolyzed water” and do not advertise that HOCl is the active ingredient in bleach (5).


III.   Evidence for HOCl Foggers

  • There is no empiric evidence to support benefits OR prove harms from using HOCl foggers in the context of COVID-19.

  • HOCl as a compound has some evidence to suggest that it is effective against COVID-19

    • Cells in vitro use Cl- ions to produce HOCl in response to viral infections; this response leads to cellular resistance to a number of types of viruses including coronavirus 229E (6).

    • Patients who received an intervention of NaCl nasal irrigation and gargle (n=7) had a shorter illness duration compared with control patients (n=8), which researchers attribute to cells using the Cl to produce HOCl to fight the virus (2).

Evidence for HOCl Foggers in Other Contexts

  • HOCl fog reduced infectivity and RNA titres of norovirus by 99.9% (7).

  • HOCl fog reduced fungal and bacterial pollution in daycares (8).

IV.   Evidence Against HOCl Foggers

  • The WHO recommends against spray or fog disinfection for COVID-19 related disinfection on the basis of the following trials:

  • Spray cleaning is less effective as a result of a spray shadow where the cleaner does not land (9). The main goal of this study was to determine a method to evaluate cleaning strategies and this finding was incidental and not evaluated statistically.

  • Healthcare worker exposure to chlorine spray during the Ebola outbreak resulted in increased eye, skin, and respiratory symptoms (10). This study evaluated healthcare workers that were directly sprayed with chlorine products.

  • Long term use of cleaning sprays has been linked to adult asthma (11, 12).

Questions? Comments? Does this need to be updated? Do you have valuable points to add ? Please email ask.reakt@ubc.ca.


  1. Cleaning and disinfection of environmental surfaces in the context of COVID-19 [Internet]. Who.int. 2018 [cited 2020 Jun 4]. Available from: https://www.who.int/publications-detail/cleaning-and-disinfection-of-environmental-surfaces-inthe-context-of-covid-19

  2. Ramalingam S, Graham C, Dove J, Morrice L, Sheikh A. Hypertonic saline nasal irrigation and gargling should be considered as a treatment option for COVID-19. Journal of Global Health [Internet]. 2020 Mar 29 [cited 2020 Jun 4];10(1). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193539/

  3. Epidem, Inf. Chemical disinfection of non-porous inanimate surfaces experimentally contaminated with four human pathogenic viruses. 1989 [cited 2020 Jun 4];102. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2249473/pdf/epidinfect00015-0129.pdf

  4. Health Canada. Hard-surface disinfectants and hand sanitizers (COVID-19) – Canada.ca [Internet]. Canada.ca. 2020 [cited 2020 Jun 4]. Available from: https://www.canada.ca/en/health-canada/services/drugs-health-products/disinfectants/covid-19.html

  5. New Sanitizing Technology Makes Quick Work of COVID-19 [Internet]. The Maritime Executive. 2020 [cited 2020 Jun 4]. Available from: https://www.maritime-executive.com/features/new-sanitizing-technology-makes-quick-work-of-covid-19-1

  6. Ramalingam S, Cai B, Wong J, Twomey M, Chen R, Fu RM, et al. Antiviral innate immune response in non-myeloid cells is augmented by chloride ions via an increase in intracellular hypochlorous acid levels. Scientific Reports [Internet]. 2018 Sep 11 [cited 2020 Jun 4];8(1). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6134045/

  7. ‌Park GW, Boston DM, Kase JA, Sampson MN, Sobsey MD. Evaluation of Liquid- and Fog-Based Application of Sterilox Hypochlorous Acid Solution for Surface Inactivation of Human Norovirus. Applied and Environmental Microbiology [Internet]. 2007 May 4 [cited 2020 Jun 4];73(14):4463–8. Available from: https://aem.asm.org/content/aem/73/14/4463.full.pdf

  8. Chen N-T, Su Y-M, Hsu N-Y, Wu P-C, Su H-J. Airborne fungi and bacteria in child daycare centers and the effectiveness of weak acid hypochlorous water on controlling microbes. Journal of Environmental Monitoring [Internet]. 2012 [cited 2020 Jun 4];14(10):2692. Available from: https://pubs.rsc.org/en/content/articlelanding/2012/em/c2em30113j/unauth#!divAbstract

  9. ‌Roth K. Inter-hospital trials to determine minimal cleaning performance according to the guideline by DGKH, DGSV and AKI [Internet]. [cited 2020 Jun 4]. Available from: https://www.researchgate.net/profile/Winfried_Michels/publication/292641729_Inter-hospital_trials_to_determine_minimal_cleaning_performance_according_to_the_guideline_by_DGKH_DGSV_and_AKI/links/571a4d4108ae7f552a472e88/Inter-hospital-trials-to-determine-minimal-cleaning-performance-according-to-the-guideline-by-DGKH-DGSV-and-AKI.pdf

  10. ‌Mehtar S, Bulabula ANH, Nyandemoh H, Jambawai S. Deliberate exposure of humans to chlorine-the aftermath of Ebola in West Africa. Antimicrobial Resistance & Infection Control [Internet]. 2016 Nov 14 [cited 2020 Jun 4];5(1). Available from: https://aricjournal.biomedcentral.com/articles/10.1186/s13756-016-0144-1

  11. ‌Zock J-P, Plana E, Jarvis D, Antó JM, Kromhout H, Kennedy SM, et al. The Use of Household Cleaning Sprays and Adult Asthma. American Journal of Respiratory and Critical Care Medicine [Internet]. 2007 Oct 15 [cited 2020 Jun 4];176(8):735–41. Available from: https://www.atsjournals.org/doi/full/10.1164/rccm.200612-1793OC

  12. ‌Schyllert C, Rönmark E, Andersson M, Hedlund U, Lundbäck B, Hedman L, et al. Occupational exposure to chemicals drives the increased risk of asthma and rhinitis observed for exposure to vapours, gas, dust and fumes: a cross-sectional population-based study. Occupational and Environmental Medicine [Internet]. 2016 Jul 27 [cited 2020 Jun 4];73(10):663–9. Available from: https://oem.bmj.com/content/73/10/663


The above is intended to serve as a rapidly-created, accessible source of information curated by medical students and healthcare professionals. It is for educational purposes only and is not a complete reference resource. It is not professional medical advice, and is not a substitute for the discretion, judgment, and duties of healthcare professionals. You are solely responsible for evaluating the information above.