Interested in Cold Fogging? Watch Dr. Lisa Germain’s Cold Fogging webinar here!

Are you taking additional infection control steps with cold fogging?

July 1, 2020
By Lisa Germain, DDS, MScD

Congratulations to the dental profession.  We won the lottery.  According to data from the Occupational Information Network, dental hygienists are the most likely of all healthcare workers to contract SARS-CoV-2 in the workplace and dentists and assistants are right behind them!  This is primarily due to the aerosols that we create when using ultrasonic scalers and highspeed handpieces.  According to the New England Journal of Medicine, viral particles stay contagious in the air for 3 hours or more.  While an N-95 mask (or KN-95) is probably our best personal protection, ultra low volume fogging with a hypochlorous acid solution is our best option at this point to “clean the air”.

In my attempt to answer your questions about cold fogging, my recent webinar raised even more about this process.  So, I will attempt to answer the new FAQ’s here.  In addition, I started a blog to address additional concerns and will be sending out a newsletter with updates and new information every week.  There is still so much we need to understand about this virus.  If you want to ask me a question, I would like to answer it on the blog, because if you are confused about something chances are, others are as well.  We are currently being bombarded with information, often contradictory, and certainly very confusing. So, the intent of the blog is to give us a place to ask and answer questions, cooperate, collaborate and share our best practices. I like to think that SARS-CoV-2 is Goliath and we are collectively, David.  And we all know how that story turned out!  To receive the newsletter and join the discussion for THE COLD FOG BLOG, please register on the home page of my website:

Hypochlorous Acid (HOCl), also known as electrolyzed water is considered by the FDA to be “the form of free available chlorine that has the highest bactericidal activity against a broad range of microorganisms” (US FDA, 2015). HOCl has no toxic material disposal requirements, and is not considered by OSHA to be hazardous waste adding yet another advantageous element to HOCl use (OSHA Hazard Communication Standard).  The additional protein denaturing activity of HOCl and in particular, its inactivation of prion proteins, also suggests new opportunities for the design and execution of disease control measures in healthcare institutions (Hughson et al., 2016).

The reason why hypochlorous acid is such an effective oxidant is because it carries no electrical charge. In contrast, the hypochlorite ion (bleach) carries a negative charge. Because germ surfaces also carry a negative charge, they initially repel each other and it takes up to half an hour for bleach to do the job.  Whereas, the hypochlorous acid’s lack of electrical charge allows it to penetrate the protective lipid barrier surrounding the viral particles quickly and to destroy the proteins in a matter of seconds. 

Hypochlorous acid, unlike chlorine bleach, is 100% safe, non-irritating and not corrosive. Various concentrations of hypochlorous acid are used in the food industry, for eye and wound care and as a surface disinfectant. So, if it gets on your skin or in your eyes, it will not burn.  Even if it were accidentally ingested, it is non-toxic.   However there are currently no studies that discuss inhalation safety, so if you do decide to use it, wearing a mask during application is advised. 

Various formulations and strengths of HOCl are registered with the EPA, and HOCl is used for disinfection and sterilization worldwide.  It is available pre-made, or you can make your own with a home electrolysis machine using water, kosher salt and vinegar.   Current recommendations for cold fogging to deviralize (is that a word?)* aerosols created in the dental office are in a concentration of 200 ppm.  The solution is a weak acid with a pH between 5-6.  There are test strips available to test the ppm, as well as ones to test the pH.

The solution is placed into the reservoir of an ultra low volume, fogging machine that will create a mist (not a spray) of the solution.  The machine that you use needs to be able to disperse the HOCl in a particle size of 20 microns, so check the specs of your device prior to use.  Surfaces to which it is applied must be clean and dry prior to cold fogging, So, wiping down your chairs, counters, lights, etc with whatever you normally use to disinfect them needs to be done before cold fogging.

Now comes the fun part. Point the fogger at one corner of the ceiling of your operatory, and begin spraying a fine mist all the way around the perimeter. Then distribute it evenly in “stripes” across the rest of the ceiling.  You can then give an extra mist over the chair area where the aerosol creation was the heaviest.  Now, don’t go all “Rambo” with it or you will create puddles.  If done correctly, it should dry in a minute or so.  You can then seat your patient.  It can be done between every patient if you choose.

While the intent is to clear the viral particles in the air, isolation gowns and shoes can safely be cold fogged with HOCl although efficacy has not been tested.  It is very important to note that N-95 masks become ineffective if they get wet.  Moisture will destroy the electrostatic charge in the filter that creates the true protective barrier between the virus and your respiratory system.  It is safe to fog your street clothing and scrubs with cold fogging, however it is not a substitute for laundering them. 

Cold fogging with electrolyzed water (HOCl) is often confused with electrostatic spraying, a method for surface disinfection and not for aerosols.   HVAC filters and room filters with hepa technology and UVC light are all great adjuncts for cleaning and recirculating the air, and can be used in conjunction as additional protection along with cold fogging.   Heat fogging uses different machinery and is not appropriate for indoor use.

And now for the 64 million dollar question: “if I do ‘X’, ‘Y’ and ‘Z’,  (you fill in your protocol), is it still necessary to cold fog with hypochlorous acid?   The bottom line is that we don’t know the answer to this question.  It is, however, a logical way to the deal with the microbes created by dental aerosols. Every clinician needs to do his or her own due diligence to establish a protocol that they feel creates a safe environment for themselves, their team and their patients.

{*I cannot find “deviralize” in any reference or dictionary…so if it becomes part of our language, remember where you heard it first!}


  1. OSHA Hazard Communication Standard: 29 CFR 1910.1200
  2. Hughson, A. G., Race, B., Kraus, A., Sangaré, L. R., Robins, L., Groveman, B. R., … Caughey, B. (2016). Inactivation of Prions and Amyloid Seeds with Hypochlorous Acid. PLoS Pathogens, 12(9), e1005914.