Disinfectant Selection and Use
Disinfectant types include alcohols, chlorinated compounds, iodophores, phenols, quaternary ammonium compounds (quat or QAC), peroxygens, and beyond. Each type has a specific effect on the microorganism (such as dissolving the lipid membrane or denaturing proteins), based on features such as: whether the virus is enveloped, the bacterium is in spore form, and more; each type of microorganism reacts differently to the disinfectant you choose. So how do you know which one to use?
Lab personnel are responsible for cleaning the surfaces and instruments in their laboratories and offices. If you don’t choose the right disinfectant, or if you don’t use it properly, you can leave contamination behind, which can lead to exposures, damage your equipment, and negatively affect your research. Disinfectants work because they are toxic to biological materials. This also means they are toxic to you. Always consult manufacturer directions to determine the efficacy of the disinfectant against the biohazards in your lab and be sure to allow for sufficient contact time. Consult manufacturer directions to determine the efficacy of the disinfectant against the biohazards in your lab and be sure to allow for sufficient contact time.
- Evaluate your biological material – Is it a lipid-enveloped virus? Vegetative bacteria? Bacterial Spore? Intracellular? The answer will influence your disinfectant selection.
- Evaluate the organic content – Are you working with blood? Cell culture? Feces? Tissue? Plants? The amount of dirt or organic load makes a big difference in whether the disinfectant will work or not, for example, bleach and quaternary ammonium compounds (quats) become inactivated in the presence of organic matter.
- Evaluate your equipment – Is the equipment sensitive to corrosivity? Can it be immersed? Are there any alternatives to chemical disinfection, such as autoclaving?
- Evaluate your options – Is a chemical disinfectant most appropriate, or would autoclaving be easier? Which disinfectant is best for your activities? Contact EHS Biosafety if you need help determining this.
- Contact time matters – A quick spray or wipe with a disinfectant is useless; each disinfectant has its own contact time; read the label of the brand you choose.
- Note on Bleach – Bleach (sodium hypochlorite) kills most organisms, however, a 1:10 dilution of household bleach (~0.5% hypochlorite) only remains effective for 24 hours. It will corrode stainless steel. To prevent corrosion in your biosafety cabinet, use a squeeze bottle of 10% bleach (rather than spray) and follow it with a 70% ethanol rinse.
- Note on Ethanol – 70% ethanol also kills many organisms, but depending on the organism you are trying to kill, it has a contact time of up to 20 minutes. Most users apply it in a way that it evaporates too quickly to be effective. If you want to use ethanol, it has to saturate and remain for prescribed contact time; this won’t happen in a biosafety cabinet because of the airflow, so either follow the note on bleach, choose an alternative disinfectant, or contact EHS for assistance.
Things to Avoid
- Do not skip your PPE – Just as disinfectants are toxic to the material you are working with, they can harm you as well. Manufacturers will include PPE recommendations with commercial disinfectants. Apply lab-made solutions of bleach or alcohols using PPE which includes gloves and eye protection.
- Do not overlook chemical reactions – Some disinfectants will interact with the chemicals you are working within the lab and result in highly toxic mixtures (e.g., bleach mixed with ammonia)– contact EHS before generating these wastes
- Do not spray in a biosafety cabinet – Spraying disinfectants, specifically bleach, allow more of the chemical to get into parts of the cabinet that you cannot access, leading to potential corrosion and recirculation back into the room. Use a squeeze bottle instead.
Where to get more information
- Review Section 3.4 of the Biosafety Manual for more information on disinfectants
- Contact EHS at askEHS@cornell.edu if you have any questions about your disinfectant needs or general waste disposal
- The Center for Food Security and Public Health at Iowa State University offers an excellent quick reference chart for disinfectant selection.
Guidance during the COVID-19 Pandemic
SARS-CoV-2 is a lipid enveloped virus and can be inactivated using many products registered in New York for use against COVID-19. Disinfect shared equipment in the lab before and after each use. Label or place a sign near the equipment with a reminder to do this. Place a spray bottle or with disinfectant and wipes near the equipment. (Don’t forget to properly label the bottle and keep a small trash can nearby for disposal of the wipes).
Disinfect benches and high touch surfaces in the lab at the start of, halfway through, and at the end of the workday. Many of these high-touch surfaces are obvious, like door handles/knobs in the lab, drawer, and cabinet handles, while others are less obvious like the outside of shared reagent bottles. Other surfaces include:
Equipment handles, latches, and touchscreen
- Hood sashes or airfoils
- Growth room or greenhouse tools
- Pipettors/pipetman and other hand tools
- Chair backs and armrests
- Freezer, refrigerator, incubator, water bath handles, and knobs
- Whiteboards, pens
- Light switches
- Computer keyboards, tablets, and cellphones
Equipment corridors and shared equipment spaces
Shared facilities and equipment, including fume hoods and biosafety cabinets, procedure rooms, instruments, and instrument/resource facilities, will require coordination with other lab groups. Locally, research groups should consider both a sign-up sheet and reservation system to book time as well as be responsible for disinfecting the space. Disinfect equipment and all touchable surfaces. Place a spray bottle with disinfectant and wipes near the equipment.