Air disinfectants Air disinfectants are typically chemical substances capable of disinfecting microorganisms suspended in the air. Disinfectants are generally assumed to be limited to use on surfaces, but that is not the case. In 1928, a study found that airborne microorganisms could be killed using mists of dilute bleach. An air disinfectant must be dispersed either as an
aerosol or
vapour at a sufficient concentration in the air to cause the number of viable infectious microorganisms to be significantly reduced. In the 1940s and early 1950s, further studies showed inactivation of diverse
bacteria,
influenza virus, and
Penicillium chrysogenum (previously
P. notatum)
mold fungus using various glycols, principally
propylene glycol and
triethylene glycol. In principle, these chemical substances are ideal air disinfectants because they have both high lethality to microorganisms and low mammalian toxicity. Although glycols are effective air disinfectants in controlled laboratory environments, it is more difficult to use them effectively in real-world environments because the disinfection of air is sensitive to continuous action. Continuous action in real-world environments with outside air exchanges at door, HVAC, and window interfaces, and in the presence of materials that absorb and remove glycols from the air, poses engineering challenges that are not critical for surface disinfection. The engineering challenge associated with creating a sufficient concentration of the glycol vapours in the air have not to date been sufficiently addressed.
Alcohols Alcohol and alcohol plus
Quaternary ammonium cation based compounds comprise a class of proven surface sanitizers and disinfectants approved by the
EPA and the
Centers for Disease Control for use as a hospital grade disinfectant. Alcohols are most effective when combined with
distilled water to facilitate diffusion through the cell membrane; 100% alcohol typically denatures only external membrane proteins. A mixture of 70%
ethanol or
isopropanol diluted in water is effective against a wide spectrum of bacteria, though higher concentrations are often needed to disinfect wet surfaces. Additionally, high-concentration mixtures (such as 80% ethanol + 5% isopropanol) are required to effectively inactivate lipid-enveloped viruses (such as
HIV,
hepatitis B, and
hepatitis C). The efficacy of alcohol is enhanced when in solution with the wetting agent
dodecanoic acid (coconut soap). The synergistic effect of 29.4% ethanol with dodecanoic acid is effective against a broad spectrum of bacteria, fungi, and viruses. Further testing is being performed against
Clostridioides difficile (C.Diff) spores with higher concentrations of ethanol and dodecanoic acid, which proved effective with a contact time of ten minutes.
Aldehydes Aldehydes, such as
formaldehyde and
glutaraldehyde, have a wide microbicidal activity and are
sporicidal and
fungicidal. They are partly inactivated by organic matter and have slight residual activity. Some bacteria have developed resistance to glutaraldehyde, and it has been found that glutaraldehyde can cause asthma and other health hazards, hence
ortho-phthalaldehyde is replacing glutaraldehyde.
Oxidizing agents Oxidizing agents act by oxidizing the cell membrane of microorganisms, which results in a loss of structure and leads to cell
lysis and death. A large number of disinfectants operate in this way.
Chlorine and
oxygen are strong oxidizers, so their compounds figure heavily here. •
Electrolyzed water or "Anolyte" is an oxidizing, acidic hypochlorite solution made by
electrolysis of
sodium chloride into
sodium hypochlorite and hypochlorous acid. Anolyte has an oxidation-reduction potential of +600 to +1200 mV and a typical pH range of 3.5––8.5, but the most potent solution is produced at a controlled pH 5.0–6.3 where the predominant oxychlorine species is
hypochlorous acid. •
Hydrogen peroxide is used in
hospitals to disinfect surfaces and it is used in solution alone or in combination with other chemicals as a high level disinfectant. Hydrogen peroxide is sometimes mixed with
colloidal silver. It is often preferred because it causes far fewer
allergic reactions than alternative disinfectants. Also used in the
food packaging industry to disinfect foil containers. A 3% solution is also used as an antiseptic. •
Hydrogen peroxide vapor is used as a
medical sterilant and as room disinfectant. Hydrogen peroxide has the advantage that it decomposes to form oxygen and water thus leaving no long term residues, but hydrogen peroxide as with most other strong oxidants is hazardous, and solutions are a primary irritant. The vapor is hazardous to the respiratory system and eyes and consequently the
OSHA permissible exposure limit is 1 ppm (29 CFR 1910.1000 Table Z-1) calculated as an eight-hour time weighted average and the
NIOSH immediately dangerous to life and health limit is 75 ppm. Therefore, engineering controls,
personal protective equipment, gas monitoring etc. should be employed where high concentrations of hydrogen peroxide are used in the workplace. Vaporized hydrogen peroxide is one of the chemicals approved for decontamination of anthrax spores from contaminated buildings, such as occurred during the
2001 anthrax attacks in the U.S. It has also been shown to be effective in removing exotic animal viruses, such as avian influenza and
Newcastle disease from equipment and surfaces. • The antimicrobial action of hydrogen peroxide can be enhanced by
surfactants and organic acids. The resulting chemistry is known as
Accelerated hydrogen peroxide. A 2% solution, stabilized for extended use, achieves high-level disinfection in 5 minutes, and is suitable for disinfecting medical equipment made from hard plastic, such as in
endoscopes. The evidence available suggests that products based on Accelerated Hydrogen Peroxide, apart from being good germicides, are safer for humans and benign to the environment. •
Ozone is a gas used for disinfecting water, laundry, foods, air, and surfaces. It is chemically aggressive and destroys many organic compounds, resulting in rapid decolorization and deodorization in addition to disinfection. Ozone decomposes relatively quickly. However, due to this characteristic of ozone, tap water chlorination cannot be entirely replaced by ozonation, as the ozone would decompose already in the water piping. Instead, it is used to remove the bulk of oxidizable matter from the water, which would produce small amounts of
organochlorides if treated with chlorine only. Regardless, ozone has a very wide range of applications from municipal to industrial water treatment due to its powerful reactivity. •
Potassium permanganate (KMnO4) is a purplish-black crystalline powder that colours everything it touches, through a strong oxidising action. This includes staining "stainless" steel, which somewhat limits its use and makes it necessary to use plastic or glass containers. It is used to disinfect
aquariums and is used in some community swimming pools as a foot disinfectant before entering the pool. Typically, a large shallow basin of KMnO4 / water solution is kept near the pool ladder. Participants are required to step in the basin and then go into the pool. Additionally, it is widely used to disinfect community water ponds and wells in tropical countries, as well as to disinfect the mouth before pulling out teeth. It can be applied to wounds in dilute solution.
Peroxy and peroxo acids Peroxycarboxylic acids and inorganic peroxo acids are strong oxidants and extremely effective disinfectants. •
Peroxyformic acid •
Peracetic acid •
Peroxypropionic acid •
Monoperoxyglutaric acid •
Monoperoxysuccinic acid •
Peroxybenzoic acid •
Peroxyanisic acid •
Chloroperbenzoic acid •
Monoperoxyphthalic acid •
Peroxymonosulfuric acid Phenolics Phenolics are active ingredients in some household disinfectants. They are also found in some mouthwashes and in disinfectant soap and handwashes. Phenols are toxic to cats and newborn humans •
Phenol is probably the oldest known disinfectant as it was first used by
Lister, when it was called carbolic acid. It is rather corrosive to the skin and sometimes toxic to sensitive people. Impure preparations of phenol were originally made from
coal tar, and these contained low concentrations of other
aromatic hydrocarbons including
benzene, which is an
IARC Group 1 carcinogen. •
o-Phenylphenol is often used instead of
phenol, since it is somewhat less corrosive. •
Chloroxylenol is the principal ingredient in
Dettol, a household disinfectant and
antiseptic. •
Hexachlorophene is a phenolic that was once used as a germicidal additive to some household products but was banned due to suspected harmful effects. •
Thymol, derived from the herb thyme, is the active ingredient in some "broad spectrum" disinfectants that often bear ecological claims. It is used as a stabilizer in pharmaceutic preparations. It has been used for its antiseptic, antibacterial, and antifungal actions, and was formerly used as a vermifuge. •
Amylmetacresol is found in
Strepsils, a throat disinfectant. • Although not a phenol,
2,4-dichlorobenzyl alcohol has similar effects as phenols, but it cannot inactivate viruses.
Quaternary ammonium compounds Quaternary ammonium compounds ("quats"), such as
benzalkonium chloride, are a large group of related compounds. Some concentrated formulations have been shown to be effective low-level disinfectants. Quaternary ammonia at or above 200ppm plus alcohol solutions exhibit efficacy against difficult to kill non-enveloped viruses such as
norovirus,
rotavirus, or
polio virus. •
Sodium hypochlorite •
Calcium hypochlorite •
Monochloramine •
Chloramine-T •
Trichloroisocyanuric acid •
Chlorine dioxide •
Hypochlorous acid Iodine •
Iodine •
Iodophors
Acids and bases •
Sodium hydroxide •
Potassium hydroxide •
Calcium hydroxide •
Magnesium hydroxide •
Sulfurous acid •
Sulfur dioxide •
phosphoric acid •
dodecylbenzenesulfonic acid It has very low toxicity to higher organisms such as human cells, which have more complex and protective membranes. Common
sodium bicarbonate (NaHCO3) has antifungal properties, and some antiviral and antibacterial properties, though those are too weak to be effective at a home environment.
Non-chemical Ultraviolet germicidal irradiation is the use of high-intensity shortwave
ultraviolet light for disinfecting smooth surfaces such as dental tools, but not porous materials that are opaque to the light such as wood or foam. Ultraviolet light is also used for municipal
water treatment. Ultraviolet light fixtures are often present in
microbiology labs, and are activated only when there are no occupants in a room (e.g., at night). Heat treatment can be used for disinfection and sterilization. The phrase "sunlight is the best disinfectant" was
popularized in 1913 by
United States Supreme Court Justice
Louis Brandeis and later advocates of
government transparency. While sunlight's ultraviolet rays can act as a disinfectant, the Earth's
ozone layer blocks the rays' most effective wavelengths. Ultraviolet light-emitting machines, such as those used to disinfect some hospital rooms, make for better disinfectants than sunlight. Since the mid-1990s
cold plasma has been shown to be an efficient sterilization/disinfection agent. Cold plasma is an ionized gas that remains at room temperature. It generates reactive oxygen and reactive nitrogen species that interact with bacterial wall and membrane and cause oxidation of the lipids and proteins and can also lyse the cells. Cold plasma can inactivate bacteria, viruses, and fungi. ==Electrostatic disinfection==