Hypochlorous acid is a free chlorine molecule with HOCl chemical structure. In chlorine solutions, they are the dominant free chlorine types that are slightly acidic to neutral pH. HOCl is a much stronger oxidant than sodium hypochlorite (or chlorine bleach).
Frequently Asked Questions
General questions
Hypochlorous acid is naturally produced by the white blood cells of all mammals. It is used by white blood cells to kill invading microbial pathogens.
Hypochlorous acid (HOCl) is a neutral charged molecule. Bacteria have negatively charged cell walls. Like magnets, molecules with the same charge repel each other. For example, the negatively charged bleach molecule (OCl-) is repelled by bacterial cell walls. This does not apply to HOCl, which is charged neutrally. HOCl bacteria easily penetrate the cell walls. HOCl either oxidizes cell walls that kill bacteria or enter cell walls and destroy vital components in bacteria.
Unlike many other sanitation chemicals, hypochlorous acid has no ongoing antimicrobial effect. In other words, when it lands on a surface, it reacts with any microbe or organic matter on that surface and immediately becomes ineffective. This is both good and bad. This is good because it allows for sanitation without the need for rinsing because no toxic chemicals are left behind. The disadvantage is that it is produced on site.
Hypochlorous acid is made by a process called electrolysis. Electrolysis water is produced by passing a sodium chloride solution (NaCl) through an electrolysis cell containing an anode and a cathode.
Hypochlorous acid can be made from chlorine bleach by dilution, but there are limitations. Hypochlorous acid is almost absent in a free chlorine solution with a pH above 9. The pH of the chlorine bleach is above 13. By diluting the chlorine bleach, the pH can be lowered, but the free chlorine concentration is also lowered. Upon dilution of chlorine bleach to pH 8.5, the percentage of free chlorine, which is hypochlorous acid, is less than 5%. Further dilution will dilute the current free chlorine concentration to unnecessary levels. Trying to lower the pH with acidifiers will also not help, since the chlorine bleach will react violently and the free chlorine product will disappear as chlorine gas. Therefore, Electrolysis is the only safe method to produce high concentration of acidic-neutral pH free chlorine solutions dominated by hypochlorous acid. At PH 5, the percentage of free chlorine, which is hypochlorous acid, is over 99%.
Chlorine is a highly effective disinfectant to neutralize bacteria. A study conducted in the 1940s investigated inertial levels as a function of time for E. coli, Pseudomonas aeruginosa, Salmonella typhi and Shigella dysenteriae (Butterfield et al. 1943). The results of the study showed that HOCl is more effective than OCl (ie chlorine bleach) in neutralizing these bacteria. These results have been confirmed by many researchers who concluded that HOCl is 70 to 80 times more effective than OCl for inactivating bacteria (Culp / Wesner / Culp, 1986). Since 1986, there have been hundreds of publications confirming HOCl’s superiority to OCl.
HOCl may be more effective than OCl – for two reasons, this is because it first holds a neutral charge, and therefore bacteria can easily penetrate into negatively charged cell walls. The second reason is that HOCl has a much higher oxidation potential than OCl-.
Hypochlorous acid (HOCl) has been investigated and proven to be effective against many viruses.
Yes, hypochlorous acid is very effective in cleaning biofilm and preventing its formation.
The concentration to be used depends on the application. Disinfection of food items such as fruits, vegetables, fish and seafood is highly effective at 20-30 ppm, but the FDA allows it to be used at concentrations as high as 60 ppm without the need for a rinse. Disinfecting food contact surfaces are also effective at 20-30 ppm, but concentrations up to 200 ppm are allowed by the FDA. Disinfection of water is effective at 1-2 ppm, but EPA allows 4 ppm. When deciding which concentration to use, it is best to refer to the research. More than 300 research articles have been published covering almost every application. How is concentration measured? Hypochlorous acid is measured with the same standard test strips that measure free chlorine in a pool. The test strips will turn to a different purple shade to indicate the concentration between 10 and 200 ppm. The solution tested for higher concentrations can be diluted. (Example: A 1000 ppm solution can be diluted 1:10. A test strip can read 100 ppm indicating that the original solution is 1000 ppm.)
More than 300 research articles have been published covering almost every application.
The most researched applications have been made in the food industry using hypochloric acid for direct food sanitation and sanitation of food contact surfaces. Other applications explored were in the field of health for disinfection and sterilization of equipment, wound care and general sanitation of healthcare facilities against MRSA and sports-forming organisms. In addition, research has been carried out for animal husbandry, agriculture and water treatment and disinfection.
Yes, probably the most research on hypochlorous acid has been done in microbial pathogens Listeria, Salmonella and E. coli.
Hypochlorous acid is very effective against MRSA. Since Clostridium specias is difficult to cultivate in the laboratory, Bacillus species are also used, which are sportive bacteria, which are more difficult to kill.
Yes, there are two published studies on Norovirus.
Safety and Environment
Hypochlorous acid is non-toxic and non-hazardous. Unlike most chemical disinfectants, hypochlorous acid is not irritating to the eyes, skin, and respiratory tract. Even if accidentally swallowed, it does not hurt.
Yes, most of the research on hypochlorous acid has been related to the direct use of hypochlorous acid in food. FDA Food Contact Notice 1811 allows the use of hypochlorous acid at 60 ppm in raw or processed fruits and vegetables, fish and seafood, meat, poultry and shell eggs.
Hypochlorous acid does not affect the taste or smell of foods when used in FDA-cleared concentrations.
Cleaning the food contact material with the FDA requires that no harmful deposits are left behind. Hypochlorous is cleaned for use up to 60 ppm.
Yes, hypochlorous acid is 100% safe and non-irritating. It is safe enough to be used in personal items for toothbrushes, baby pacifiers and pets.
Hypochlorous acid is less aggressive in fabrics than peroxide or chlorine bleach. Although hypochlorous acid does not usually cause bleaching or discoloration, some poor-quality dyes may bleed when exposed to hypochlorous acid.
Hypochlorous acid is a strong oxidant and causes corrosion if prolonged exposure to brass, copper, iron, or poor quality steel. Stainless steel can corrode when immersed in high concentrations of hypochloric acid (> 200 ppm) for a long time.
Industry and Application
Hypochlorous acids (HOCl) are used in restaurants, food and beverage processing, animal husbandry, agriculture, hospitals, schools, cruise ships, water treatment and drug production.
Hypochlorous acid (HOCl) is used by restaurants as a rinse-free disinfectant for meat, poultry and seafood. HOCl prolongs shelf life. HOCl is used for cleaning all kitchen utensils, cutting boards, cutlery and utensils, as well as for cleaning surfaces that come into contact with food. HOCl makes a great hand sanitizer. It also replaces toxic chemicals used in sink, bathroom and floor cleaning. HOCl is used to clean the restaurant’s tables and seating areas. It can be applied with hoses or foggers to disinfect large areas in general.
Hypochlorous acid (HOCl) replaces water in product washers and extends shelf life to clean and disinfect fruits and vegetables as a non-rinsing disinfectant. HOCl is used to sterilize equipment and work areas. HOCl can be applied through hoses or foggers to generally sterilize large areas. Employees can enter foot baths and be misted by HOCl when entering a processing facility.
Hypochlorous acid (HOCl) is safe on animals and has many applications in the poultry industry, including hatcheries, broilers and processing. HOCl can be applied to the eggs by steaming in hatcheries and cleaned with FDA FCN 1811. Hypochlorous acid can be applied to drinking water at 4 ppm for broiler rooms to provide sterile water. It can be applied with sprinklers and mysteries to provide a clean environment for chickens, increase growth rates and reduce feed to growth rates. HOCl can be used to sterilize whole or processed chickens as a non-rinsing sanitizer during processing using concentrations up to 60 ppm according to FDA FCN 1811. Employees can enter foot baths and be misted by HOCl when entering a processing facility.
Hypochlorous acid (HOCl) is safe on animals and has many applications for livestock and meat processing. Hypochlorous acid can be applied to living spaces to protect clean and disinfected environments. HOCl can be applied to water for sterile drinking water. HOCl is used to sterilize untreated crocuses as a non-rinsing disinfectant for processing. HOCl can be applied through hoses or foggers to generally sterilize large areas. Employees can enter foot baths and be misted by HOCl when entering a processing facility.
Hypochlorous acid (HOCl) can be used in harvesting and processing to sterilize raw seafood as a non-rinsing disinfectant up to 60 ppm according to FDA FCN 1811. It can be applied with hoses to clean equipment and sterilize work areas. Employees can enter foot baths and be misted by HOCl when entering a processing facility.
Hypochlorous acid (HOCl) can produce sterile water for milk and beverage production. HOCl is used to disinfect bottles. HOCl can remove biofilm and disinfect pipes in clean systems on site. It can be applied with hoses to clean equipment and sterilize work areas. Employees can enter foot baths and be misted by HOCl when entering a processing facility.
Hypochlorous acid (HOCl) can be used to sterilize bed sheets. HOCl can be used to disinfect contact surfaces and can be widely applied to rooms and common areas through foggers. HOCl replaces concentrated toxic chemicals to clean and disinfect sinks, bathrooms and floors. HOCl can be used as a hand sanitizer for staff and guests through dispensers.
Hypochlorous acid has many beneficial applications on a cruise ship. HOCl can be used as a non-rinsing disinfectant for products, meat, poultry and seafood in the kitchen. HOCl can be used on food contact surfaces and as a disinfectant for general sanitation instead of disinfection and peroxide-based chemicals. It can be applied through foggers or misters to disinfect the rooms and large common areas widely. HOCl can be used to clean and disinfect the ship for the prevention and control of Norovirus outbreaks. HOCl can be used as hand sanitizers through dispensers throughout the ship. HOCl can replace chlorine to produce drinking water and pool treatment.
Hypochlorous acid (HOCl) replaces chlorine in pool therapy. HOCl is not irritating and safe on eyes and skin.
Hypochlorous acid (HOCl) can be used to sterilize bed sheets. HOCl can replace toxic concentrated chemicals to clean and disinfect chambers and common areas. HOCl can be applied with foggers to disinfect rooms and air. HOCl can be used as a non-rinsing disinfectant for product, meat, poultry and seafood in hospital kitchen. It can be used to clean and disinfect all contact surfaces and utensils. HOCl can be placed in dispensers for hand cleaning throughout hospitals.
Hypochlorous acid (HOCl) can be used to protect sterile environments for pharmaceutical production. HOCl comes out of the biofilm site and disinfects pipes for clean-in-place (CIP) systems. HOCl can be used for cold sterilization of equipment and devices.
Hypochlorous acid (HOCl) can replace toxic concentrated chemicals to clean and disinfect school rooms and common areas. HOCl can be applied with foggers to disinfect rooms and air. HOCl can be used as a non-rinsing disinfectant for products, meat, poultry and seafood in school kitchen. It can be used to clean and disinfect all contact surfaces and kitcheware. HOCl can be placed in dispensers for hand cleaning across schools.
Hypochlorous acid is safe on animals and can replace chemicals used to sterilize habitats in the zoo.
Hypochlorous acid is ideal for CIP systems. Hypochlorous acid comes out of the biofilm and disinfects the pipes.
Regulation
Hypochlorous acid cleaned with FDA according to FCN 1811 to be used for the following applications up to 60 ppm: Hypochlorous acid can be used in process processes up to 60 ppm in processing plants; spraying, washing, rinsing, dipping, cooling water and scalding water for whole or cut meat and poultry, including carcasses, parts, mowing and organs; in process water, ice or brine used for washing, rinsing or cooling pre-formed meat and poultry products as described in 21 CFR 170.3 (n) (29) and 21 CFR 170.3 (n) (34) respectively; in process water or ice to wash, rinse or cool fruit, vegetables, whole or cut fish and seafood; and in process water to wash or rinse the shelled eggs.
The maximum concentration that can be used directly in food as a non-rinsing cleaning agent is 60 ppm in FDA FCN 1811.
The maximum concentration that can be used on food contact surfaces is 200 ppm per EPA.
Hypochlorous acid does not require after rinsing while sterilizing food at 60 ppm or below.
On June 9, 2014, the National Organic Program (NOP) issued a policy statement explaining that electrolyzed water (hypochloric acid) is allowed for organic production and use.
EPA allows the use of hypochlorous acid to disinfect drinking water at a concentration of up to 4 mg / L (or 4 ppm).
Hypochlorous Acid Application Areas
