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Safety & Use Guide

Practical, plain-language guidance for using HOCl well. Always follow your product label and Safety Data Sheet (SDS) first.

The basics

HOCl works most reliably on surfaces that have been pre-cleaned of visible soil, applied at the concentration the label specifies, and left wet for the full contact time. Organic matter uses HOCl up (CDC 2008, p. 41; Zhang 2016), and Japan’s NITE judged HOCl water effective on objects only when soil was removed first and enough volume was used (NITE 2020).

Understanding concentration

Concentration is expressed in ppm of available chlorine. Use the concentration on your product’s label. For context, here is what published studies tested:

StudyOrganismConcentrationContact timeResult
Park 2007Human norovirus20–200 ppm10 min≥3-log on tile and steel
Zhang 2016Bacillus spores60–120 mg/L2–6 minNon-detectable; soil reduced effect
Miyaoka 2021Influenza, coronavirus62–540 ppm30 s–20 minFast in suspension; carriers and wipes resisted
Hamilton 2023SARS-CoV-2 surrogate500–1000 ppm5–60 sMax 3.31 log; short sprays may fall short

Most users stay at or below 500 ppm; CDC lists hypochlorites’ “corrosiveness to metals in high concentrations (>500 ppm)” (CDC 2008, p. 41). Keep pH at 4 or above, with a target of 5–6 (Wang 2007; Takeda 2021).

How to apply

  1. Clean first. Remove visible soil; organic matter uses up HOCl.
  2. Apply generously by spray, wipe or soak so the surface stays visibly wet. Used wipes can hold virus, so don’t reuse them (Miyaoka 2021).
  3. Wait the full contact time on the label. “Spray and wipe” after a few seconds is often not enough (Hamilton 2023).
  4. Air dry or wipe as the label directs.

Storage & shelf life

HOCl is reactive, so it gradually loses strength, faster with light and heat (Reis 2021). Products at pH 5.0–6.4 kept their chlorine and activity for 21 days in one study, while those at pH 3.0 or below lost chlorine quickly (Takeda 2021).

  • Store in closed, opaque containers, away from sunlight and heat.
  • Label containers with the date made and the concentration.
  • Check strength with free-chlorine and pH test strips if in doubt.

Do’s and don’ts

Do

  • Follow the label and SDS
  • Pre-clean visibly dirty surfaces
  • Keep surfaces wet for the full contact time
  • Store out of reach of children and pets

Don’t

  • Mix with strong acids, ammonia or other cleaners
  • Let pH drop below 4
  • Fog or mist unless a product label allows it (EPA fogging FAQ)
  • Drink it or apply generator output to people or animals (EPA device guide)

When to take extra care

Wear eye protection and chemical-resistant gloves when handling concentrates, salt or acid additives, or anything above everyday surface strength, and ventilate. Mixing chlorine products with any acid or acid-containing product, or with ammonia, releases chlorine gas, which irritates eyes, nose and throat at low levels (NIOSH chlorine); US poison centers logged 85,104 chlorine and chloramine gas exposures from 2015–2022, mostly at home from mixing cleaners (Atalla 2024).

If exposure causes irritation, move to fresh air, follow the first-aid instructions on the SDS, and seek medical advice if symptoms persist.

Food-contact surfaces

EPA regulations exempt hypochlorous-acid residues from a food tolerance when HOCl is used in an antimicrobial pesticide formulation on food-contact surfaces, at no more than 200 ppm total available chlorine and with adequate draining (40 CFR 180.940(a)). Rinse and drain directions come from the registered product’s label. The same entry covers sodium hypochlorite, and other sanitizer chemistries are listed too.

A note on drinking water

EPA limits chlorine in drinking water to 4 ppm (4.0 mg/L) (EPA NPDWR).

Sources

  1. Rutala WA, Weber DJ, Healthcare Infection Control Practices Advisory Committee (HICPAC). Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008 (last update June 2024). CDC. www.cdc.gov/infection-control/media/pdfs/Guideline-Disinfection-H.pdf. guidance
  2. NITE (National Institute of Technology and Evaluation, Japan). Final report on the efficacy of alternative disinfection methods against SARS-CoV-2. June 26, 2020. www.nite.go.jp/information/osirase20200626.html. government report
  3. Zhang C, Li B, Jadeja R, Hung YC. Effects of electrolyzed oxidizing water on inactivation of Bacillus subtilis and Bacillus cereus spores in suspension and on carriers. J Food Sci. 2016;81(1):M144-M149. doi.org/10.1111/1750-3841.13169. PMID 26642381. suspension + carrier
  4. Hamilton AN, Chandran S, Baker CA, Gibson KE. Surface inactivation of a SARS-CoV-2 surrogate with hypochlorous acid is impacted by surface type, contact time, inoculum matrix, and concentration. Food Environ Virol. 2023;15(2):116-122. doi.org/10.1007/s12560-023-09549-0. PMID 36680664. carrier (surface)
  5. Miyaoka Y, Kabir MH, Hasan MA, et al. Virucidal activity of slightly acidic hypochlorous acid water toward influenza virus and coronavirus with tests simulating practical usage. Virus Res. 2021;297:198383. doi.org/10.1016/j.virusres.2021.198383. PMID 33705798. suspension + carrier
  6. Wang L, Bassiri M, Najafi R, et al. Hypochlorous acid as a potential wound care agent: Part I. J Burns Wounds. 2007;6:e5. pubmed.ncbi.nlm.nih.gov/17492050/. PMID 17492050. (authors from the product developer) review
  7. Takeda Y, Matsuda S, Jamsransuren D, Ogawa H. Comparison of the SARS-CoV-2-inactivating activities of the differently manufactured hypochlorous acid water products with various pH. J Water Health. 2021;19(3):448-456. doi.org/10.2166/wh.2021.260. PMID 34152297. in vitro
  8. Reis R, Sipahi H, Dinc O, et al. Toxicity, mutagenicity and stability assessment of simply produced electrolyzed water as a wound healing agent in vitro. Hum Exp Toxicol. 2021;40(3):452-463. doi.org/10.1177/0960327120952151. PMID 32909829. cell culture
  9. NIOSH Pocket Guide to Chemical Hazards: Chlorine (CAS 7782-50-5). www.cdc.gov/niosh/npg/npgd0115.html. guidance
  10. Atalla A, Shulman J, Rose J, Lynch M. Trends in chlorine and chloramine gas exposures reported to US poison centers. Clin Toxicol. 2024;62(9):589-595. doi.org/10.1080/15563650.2024.2390139. PMID 39263698. surveillance data
  11. EPA. Can I use fogging, fumigation, or electrostatic spraying or drones to help control COVID-19? www.epa.gov/coronavirus/can-i-use-fogging-fumigation-or-electrostatic-spraying-or-drones-help-control-covid-19. guidance
  12. EPA. Pesticide Devices: A Guide for Consumers. www.epa.gov/safepestcontrol/pesticide-devices-guide-consumers. guidance
  13. 40 CFR 180.940(a): Tolerance exemptions for active and inert ingredients for use in antimicrobial formulations (food-contact surface sanitizing solutions). www.ecfr.gov/current/title-40/chapter-I/subchapter-E/part-180/subpart-D/section-180.940. regulation
  14. EPA. National Primary Drinking Water Regulations (Chlorine as Cl2, MRDL 4.0 mg/L). www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations. regulation