General Guidelines for Effectiveness & Safety
Consumer-level Chlorine Dioxide products have a high range of safety for human health and the environment. Below are general principles for use with many Chlorine Dioxide products.
Do carefully read your product’s label to learn specific guidance for that particular product. Stronger precautions may be listed on the label, and should then be followed instead. The guidance listed here should not be regarded as authoritative or expert.
Double-check measurements for ingredients
Most consumer-level products come in user-friendly packaging and with fairly straightforward mixing requirements, and some types of commercial products are also packaged for easy mixing.
Amounts to mix are different for each product. Figuring appropriate amounts to mix can be very complex for some commercial products, particularly when mixing small or extra-large batches. It is useful to write down amounts and double check them before mixing. You can use calculators on the internet to convert measurements between units, where needed.
If desired, you can buy test strips to monitor concentrations, but need to be sure to buy ones that work with the particular product you are using.
Keep careful track of “activation” time when mixing
Some Chlorine Dioxide products are "activated" by combining Sodium Chlorite (which is not the same as Sodium Hypochlorite) with a small amount of acid, such as citric acid.
If a product requires you to mix ingredients, read instructions and add ingredients in the order specified, and carefully allow correct amount of time between adding the next ingredient. Waiting too short of too long of time impacts the level of activation and how strong the resulting solution will be. Check instructions to see if you need to wait some time after mixing, or if you can use right away.
Do not inhale gas when mixing
When Chlorine Dioxide is being initially “activated”, it releases strong fumes. Do not inhale fumes, and if you are mixing large amounts, work in a well-ventilated area. Gas fumes will stop releasing potently when you add water to the activated mixture.
Use products designed for non-occupied areas only in non-occupied areas
“Shock” or “bomb” or gassing products that release in 24 hours or less should ONLY be used when an area is unoccupied. The room should be aired out afterwards before people enter.
If a handheld fogger of high-concentration disinfectant is being used, people in the area should use appropriate PPE.
Maintain appropriate concentration levels in air
When using a slow-release (multi-day) deodorizer product, be sure the room is large and there is enough ongoing air flow so that the concentration will continually be low.
In appropriate amounts, Chlorine Dioxide can be applied to the air via humidifiers or HVAC systems in occupied rooms, to disinfect air and surfaces. Ultrasonic humidifiers are ideal. Treatment will be more effective if the humidity level in the room is high—preferably 45-65%. (Distilled water should be used in these if you may be sensitive to minerals in air.)
Note: Humidity itself also helps reduce virus transmission and provide moisture that helps your body repel pathogens. However, humidifiers can grow significant harmful bacteria if not thoroughly disinfected at least every three days. Simply adding even a small amount of Chlorine Dioxide in the humidifier tank will prevent that concern, prevent biofilms from forming, and help avoid mold problems.
How can you know how much Chlorine Dioxide to put in a humidifier?
NIOSH recommends an exposure limit of 0.3 mg/m3 or 0.1 ppmV (which is different than the ppmW in the liquid mix being used) over the course of an 8-hour work day, or 0.3 ppmV for 15-min. exposure.
See our Chlorine Dioxide Solution Calculators to figure possible concentrations to use in humidifiers.
You can also emit pure chlorine dioxide gas from a bowl of Chlorine Dioxide liquid solution. Use our Calculators to help estimate the appropriate amount to use in the room for a 30-minute interval. (Do not use more at one time or air concentration might reach too high to quickly.) Pour a corresponding amount of solution in the bowl and use an aquarium air pump and air line to aerate the solution. Exchange with fresh solution every 30 minutes.
Be sure Chlorine Dioxide will make direct contact with germs
Disinfection will not occur in gaps between droplets. It is best to use a spray bottle that gives a very fine mist, or an ultrasonic humidifier, for more thorough coverage of air and surfaces. Gas in air spreads even more evenly.
Note: Spraying will not be as thorough on surfaces if mist is not close enough or dense/thick enough to cover them well. You may wish to also spread liquid more fully over some surface areas using your hand or a dampened cloth.
Protect from sunlight, heat, moisture, and excessive shaking
UV rays from sunlight cause Chlorine Dioxide’s chemical actions to accelerate greatly. Its effectiveness will be used up very quickly if it is kept exposed to sunlight. Store it protected from sun, and always keep it in non-transparent containers, or keep containers covered well.
To prevent chemical activity from speeding up and becoming depleted or bursting the container, do not store in hot environments such as parked cars.
Prevent condensation from reaching materials prior to use. Moisture may start premature activation.
Avoiding vigorous stirring and pouring, and keeping a lid on containers will also help Chlorine Dioxide gas stay in liquid solutions longer and extend the life of the product.
Dispose of leftovers
Chlorine Dioxide's chemical activity level decreases over time. The effectiveness of most products that involve mixing to activate is usually substantially reduced within 5 to 14 days after mixing. Some products are effective for longer times. Read the product descrition to see how long a specific product is formulated to be effective. When you activate a product, write an appropriate “expiration date” on the container.
Try to only mix the amount you know you will use in the next several days, and mix up more later if needed. Do not be tempted to keep a liquid mix after your expiration date; it may no longer kill pathogens sufficiently.
Once Chlorine Dioxide’s activity level has decreased, it is relatively safe for the environment, as it mostly turns to inert salt. To neutralize it further, you can put any leftover mix in sunlight for an hour, and then pour it down the drain.
If you get a high concentration in your eyes, rinse them.
Accuracy of basic concentration levels is important, and different parts of the body have different sensitivities to Chlorine Dioxide. However, at the diluted concentrations used for general disinfection, risks to the body are quite low.
For eyes, Chlorine Dioxide is actually classed as only a mild irritant at low concentrations. It is gentle enough that Chlorine Dioxide is used as an ingredient in some contact lens care solutions.
Don’t use over-concentrated mixes for the wrong type of use
Do not use Chlorine Dioxide at much higher levels of concentration than are recommended for that specific purpose for that specific product. If a lower concentration is needed, appropriately dilute a small portion of the more concentrated mixture.
Chlorine Dioxide retains its potency better in somewhat dirty water than some other disinfectants. Also, Chlorine Dioxide’s effectiveness is fairly consistent across a broad pH range, though adjustments should be made for some highly specific situations and for significantly high or low temperatures.
You do not need to rinse or wipe off
Let surfaces air dry after applying. Chlorine Dioxide kills pathogens rapidly, but allowing liquid solutions to air dry after applying gives it maximum time for best effectiveness. Chlorine Dioxide liquid mixes will not leave noticeable or harmful residue, and effects on skin are mild, so they do not need to be rinsed off.
(Fresh produce should only be treated with very low-level ~5 ppm concentrations. Optionally, after appropriate contact time they may be rinsed off, if desired.)
* * * * *
If precautions listed on a more authoritative document or on a particular product are stronger, you should follow the stronger precautions.
The US EPA's RED document for Chlorine Dioxide and Sodium Chlorite lists some ranges of concentrations (which must be adjusted depending for every specific product's customized formulation) and specific safety limits for various uses of Chlorine Dioxide.
Visit our Related Studies page for additional research, data and government guidelines for more information on safe, effective uses of Chlorine Dioxide.