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Quaternary ammonium compounds (often called quats or QACs) are a broad class of chemicals used mainly as the active ingredient in surface disinfectants, sanitizers and wipes. The CDC states that they are “widely used as disinfectants,” and its guideline also spells out what they do not kill.
This page describes products and general use; it is not medical advice.
Who uses them: environmental services and cleaning staff, clinic and laboratory staff, and buyers who specify disinfectant wipes and sprays for healthcare and laboratory settings.
What quaternary ammonium compounds are
A quaternary ammonium compound is a chemical built around a nitrogen atom that carries four organic groups and a negative partner ion. Toxics Use Reduction Institute (TURI, University of Massachusetts Lowell) describes QACs as “a broad class of several hundred chemicals,” used mainly as active ingredients in antimicrobials, disinfectants, sanitizers and surfactants, and also found in wood preservatives, herbicides, eye drops, mouthwashes and fabric softeners.
In disinfectant products the quat is the active ingredient, usually combined with water, cleaning agents and other ingredients. TURI notes that products often contain several different QAC substances.
How they are built and how they work
The CDC Guideline for Disinfection and Sterilization in Healthcare Facilities describes quats as organically substituted ammonium compounds in which four substituents (R1 to R4) are alkyl or heterocyclic groups of a given size or chain length, and the fifth position (X-) is a halide, sulfate or similar radical. The CDC adds that each compound exhibits its own antimicrobial characteristics, so two quat products are not automatically interchangeable.
The CDC gives the mode of action as inactivation of energy-producing enzymes, denaturation of essential cell proteins, and disruption of the cell membrane.
Named compounds and families
| Compound or family | What the source says | Source |
|---|---|---|
| Alkyl dimethyl benzyl ammonium chloride (ADBAC) | One of the three quats named by the CDC as used in healthcare disinfectants | CDC 2008 guideline; TURI |
| Alkyl didecyl dimethyl ammonium chloride / didecyl dimethyl ammonium chloride (DDAC) | Named by the CDC as used in healthcare disinfectants; TURI lists DDAC as an example QAC | CDC 2008 guideline; TURI |
| Dialkyl dimethyl ammonium chloride | Named by the CDC as used in healthcare disinfectants | CDC 2008 guideline |
| Twin-chain or dialkyl quats (“fourth generation”), e.g. didecyl dimethyl ammonium bromide and dioctyl dimethyl ammonium bromide | CDC: “purportedly” remain active in hard water and are tolerant of anionic residues | CDC 2008 guideline |
| Benzalkonium chloride | The CDC reports a few case reports of occupational asthma after exposure | CDC 2008 guideline |
Quaternary ammonium uses
The CDC says quats are commonly used in ordinary environmental sanitation of noncritical surfaces such as floors, furniture and walls. It adds that EPA-registered quaternary ammonium compounds are appropriate for disinfecting medical equipment that contacts intact skin, for example blood pressure cuffs.
The CDC also reports a study of computer keyboards in which quat, 70% isopropyl alcohol, phenolic and chlorine (80 ppm) wipes each removed or inactivated more than 95% of MRSA, VRE and P. aeruginosa after a 5-second application, with no functional damage after 300 applications. Outside healthcare, TURI lists the wider uses noted above, from mouthwashes to fabric softeners.
What they do not kill
According to the CDC, quats sold as hospital disinfectants are generally fungicidal, bactericidal and virucidal against lipophilic (enveloped) viruses. They are not sporicidal, and they are generally not tuberculocidal or virucidal against hydrophilic (nonenveloped) viruses. TURI summarizes the same pattern as effective against most vegetative bacteria, enveloped viruses and some fungi.
| Target group | CDC statement for hospital-use quats |
|---|---|
| Fungi | Generally fungicidal |
| Bacteria | Generally bactericidal |
| Enveloped (lipophilic) viruses | Generally virucidal |
| Nonenveloped (hydrophilic) viruses | Generally not virucidal |
| Mycobacteria (tuberculocidal) | Generally not tuberculocidal |
| Bacterial spores | Not sporicidal |
The CDC also notes that attempts to reproduce manufacturers’ bactericidal and tuberculocidal claims with AOAC tests occasionally failed, with results varying among laboratories. For the wider question of matching a disinfectant to a surface and a contact time, see the guide on surface disinfectant selection, and for the level of disinfection needed for reusable devices, high-level disinfection and the Spaulding classification.
What reduces their effectiveness
The CDC reports that high water hardness, and materials such as cotton and gauze pads, can make quats less microbicidal, because of insoluble precipitates or because cotton and gauze absorb the active ingredient. In one study the CDC cites, the concentration of quat released was about 40% to 50% lower at 1 hour with cotton rags or cellulose wipers in an open-bucket system than with nonwoven spunlace wipers in a closed-bucket system.
The practical point is that the wipe or cloth is part of the system. A quat solution is not the same product once it has soaked into the wrong cloth.
Safe use and handling basics
- Follow the product label. The CDC notes that EPA regulates environmental-surface disinfectants under FIFRA, and that the label states it is a violation of federal law to use the product in a manner inconsistent with its labeling. Not following the use-dilution, contact time or method of application is misuse.
- Read the safety data sheet for the specific product. Products often contain more than one quat, plus other ingredients (TURI). The Hazard Communication Standard in the laboratory explains how SDSs fit into workplace safety programs.
- Treat skin and airway exposure seriously. TURI links QACs to respiratory irritation and inflammation, including an increased risk of asthma from chronic occupational exposure, calls them highly irritating to skin, and notes possible sensitization and allergic dermatitis. It describes evidence on reproductive and developmental effects as not yet conclusive. See also lab PPE.
- Where a quat wipe is used inside or around a biosafety cabinet, see the guide on biosafety cabinet cleaning and decontamination.
Common mistakes
- Assuming a quat kills everything. It is not sporicidal and generally not tuberculocidal or virucidal against nonenveloped viruses (CDC).
- Using the wrong cloth. Cotton, gauze and cellulose can absorb the active ingredient (CDC).
- Ignoring water hardness. The CDC lists high water hardness as a cause of reduced activity.
- Letting in-use solutions become a reservoir. The CDC reports healthcare-associated infections from contaminated quaternary ammonium solutions used to disinfect patient-care supplies or equipment such as cystoscopes or cardiac catheters, and that gram-negative bacteria can survive or grow in them.
- Using the product off-label. Dilution, contact time and application method on the label are part of the legal use (CDC, citing FIFRA).
FAQ
What is quaternary ammonium used for?
Mainly as the active ingredient in disinfectants and sanitizers for noncritical surfaces such as floors, furniture and walls, and for equipment that touches intact skin, such as blood pressure cuffs (CDC). TURI also lists surfactant and consumer uses.
Does quaternary ammonium kill spores?
No. The CDC states that hospital quats are not sporicidal.
Are all quats the same?
No. The CDC says each compound exhibits its own antimicrobial characteristics, and TURI describes a class of several hundred chemicals.
Sources
- Centers for Disease Control and Prevention, Guideline for Disinfection and Sterilization in Healthcare Facilities (2008, PDF footer “Last update: June 2024”), section “Quaternary Ammonium Compounds” and regulation section. https://www.cdc.gov/infection-control/media/pdfs/Guideline-Disinfection-H.pdf. Date checked: 2026-10-29.
- Toxics Use Reduction Institute, University of Massachusetts Lowell, Quaternary Ammonium Compounds Fact Sheet. https://turi.org/TURI_Publications/TURI_Chemical_Fact_Sheets/Quaternary_Ammonium_Compounds_Fact_Sheet. Date checked: 2026-10-29.
