Thursday, September 21, 2023


Formaldehyde fumigation of RV – How can I do this myself?

Dear Dave,
What are the measurements for the ammonia carbonate, charcoal and water [for the “Stink Bomb” you used at Winnebago to fumigate new RVs]. We really need to try this because our RV has a very bad chemical odor. Thanks for your blog. It’s very helpful and informative! —Cris

Dear Readers,
This question came as a recent comment regarding my post of April 22, 2022, The hidden danger of formaldehyde in RVs. I thought it would be a good topic to readdress and give the procedure as well as a few new products I have come across.

The procedure we used at Winnebago Industries was called Free Formaldehyde Abatement Procedure and was designed to eliminate noticeable formaldehyde fumes from RV products. You can read the deep dive into what causes formaldehyde fumes in RVs in the post linked above.

The short version is, any glue or other adhesive used in the production of an RV such as cabinets, carpets with glued backing material, sidewalls, and other components can produce formaldehyde fumes. In cheaper, price-point units, especially trailers, glue is still being used as it takes less time to glue rather than fasten components in a more residential construction manner.

Ammonia fumigation

The procedure we used at Winnebago was an ammonia fumigation that caused a chemical formation of an odorless crystalline solid. It is not visible, but combines with the free formaldehyde to form hexamethylenetetramine. The ammonia fumigation is accomplished by evaporating up to 3 quarts of aqueous ammonia in the unit for a period of 24 hours or more. I was able to get my hands on a copy of the original procedure that was stamped May 21, 1992. One thing I did not see in the procedure was the charcoal, which I was sure we used in a separate container.

Materials required


Use flat-bottom plastic containers capable of holding 1 gallon of liquid. Small dishpans are ideal. We actually had several black hog water bowls that worked well, and since we were in rural Iowa, they were all over the place! You will want at least one container for every 18 feet or more, depending on your floorplan. If you have divided rooms, you will want one in each room. You can get them on Amazon here.

Plastic sheets

Place a 4’x4’ plastic sheet at least 4 mil thick underneath each of the bowls. Depending on the size of your RV, you will want to use at least three bowls, one in the bedroom, one in the kitchen, and the third in the living room. If your rig is over 35 feet, you might want to add a fourth bowl.

Personal Protective Equipment (PPE)

Handling of the ammonia must be performed with caution and with the proper Personal Protective Equipment (PPE), starting with an ammonia fume respirator. This is much more robust than the N95 for COVID. We had 3M paint masks with filters that were good for paint fumes as well as ammonia, mold, and other toxic materials. There are several on the market however you want one that is a fully enclosed respirator with filters such as this one on Amazon.

You will also want non-vented chemical approved eye goggles and protective gloves.

Electric fan

Use an 8” or larger electric fan to move the ammonia fumes around to penetrate the wood and fabrics to create the hexamethylenetetramine. Depending on the size of your unit and the floorplan, I would suggest one fan for each pan you are using. We used oscillating pedestal fans, secured with a sock filled with sand at the base. They were high enough (3’) to not hit the pans and splash the liquid, but moved back and forth to provide superior air movement.

Aqueous ammonia

One gallon 26-degree Baume Ammonium Hydroxide. (Analysis on the bottle should read 28-30% NH3 or 58% NH4OH.)


Read the first aid instructions on the aqueous ammonia and be prepared to act fast if required. The handling of this type of ammonia must be performed with caution as the ammonia fumes are strong irritants to both nose and eyes as well as damaging to skin and eye tissue, should splashing or spills occur. Seek immediate medical attention to minimize tissue damage should aqueous ammonia accidentally enter the eyes. Lack of proper medical care may result in permanent vision impairment. As an added precaution, two people should be present when the aqueous ammonia is distributed in the container—one person inside, the other one outside to assure the person inside exits the RV safely.

Ammonia fumigation procedure

Prepare the RV interior for ammonia fumigation as follows:

  1. Remove all living things, plant and animal.
  2. Remove all prescription drug and any other drugs not in tightly sealed containers.
  3. Turn off all appliances and the main liquid propane (LP) valve at the tank or cylinder.
  4. Remove all food items in cupboards, pantry, and refrigerator.
  5. Remove all clothing, bedding, and towels, or seal them in plastic to reduce odor absorption.
  6. Remove all natural oak furnishings such as chairs, frames, or decorative items – ammonia may slightly darken the wood finish. This may be an unavoidable effect to cabinetry.
  7. Open all internal passages, cupboard and cabinet doors/drawers, to assure a complete    circulation of fumes throughout the RV.
  8. Lift the bed, extend the slide rooms, and pull out the sofa if applicable.
  9. Affix signs on all entrance doors: “Warning – Do Not Enter– Ammonia Fumes”.
  10. Check all windows and roof vents to assure they are closed.
  11. Remove any roof air conditioner return air vent covers and take out the filter.
  12. Plug electric fan into a non-GFCI outlet and place the fan/s far enough away to not splash the liquid.
  13. Place a 4’ x 4’ plastic sheet on the floor where each container will be placed.
  14. Put on all personal protection equipment.
  15. Hold the aqueous ammonia container at arm’s length away from your face in an upright position, slowly remove the cap or seal making sure there is no pressure inside the container, and pour approximately 1 quart in each plastic container. There should be approximately 1/2” of ammonia in the container, do not add anything else such as water or bleach.
  16. Lock any door other than the one you are exiting from, turn on the fans and quickly exit the RV.
  17. Lock the exit door and make sure the warning signs are in place.
  18. Allow the fumigation process to work for at least 24 hours in temperatures above 60 degrees. Do not fumigate in temperatures below 50 degrees.

Clean Up Procedure

  1. After the fumigation period, remove all warning signs, unlock and open entry doors and allow the unit to vent for 1 hour.
  2. Wearing recommended PPE, enter the RV and open windows and all roof vents to assist in the airing of the RV.
  3. Remove the containers on the floor. Any remaining liquid in the containers at this time will be predominately water and can be safely poured down a drain.
  4. Allow the unit to air or vent for a few more hours until the ammonia smell is not detected. This could take several hours, depending on the number of containers used.
  5. Unit is now fumigated. However, the unit may develop traces of reoccurring low levels of ammonia smells which may require additional venting.

Alternative Methods

For the most part, room air fresheners, odor-masking agents, and even ozone-generating methods have not been successful. However, last year at the Hershey RV Show I came across a product that I think might work. The product is called Go Green Environmental Inc. and the CEO was demonstrating how this air purification system could dissipate the smell of ammonia poured on a paper towel in less than 60 seconds. Keep in mind, this was at the height of the COVID pandemic. It claimed to remove 99% of airborne bacteria as well. The website also states it will remove formaldehyde, mold, and mildew.

There is a larger model that is the size of a typical portable heater that can do 3000 square feet, and a smaller model that will do 500 square feet, which is the size of a typical RV. The larger unit has been around for over 40 years. I remember the service station I worked for had one that we used to get rid of cigarette smoke in cars and it was amazing. I have not been able to test it, but you can check it out here.

 You might also enjoy this from Dave 

Black tank still smells after trying EVERYTHING

Dear Dave, 
Not sure of the year of the RV. I am having very strong odors after flushing and I have cleaned the black tank with EVERYTHING. I have had it flushed and all seems well, but in a day or two it is back to being foul. I’m thinking it is the filter or siphon but I do not know where to locate these and pinpoint which it is. Why does my black tank always smell? —Heather, Wilderness Advantage Extreme Edition

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


  1. Anyone considering this had better wear the proper recommended PPEs and don’t play he-man like you are somehow immune from it. Ammonia fumes will send you right to the hospital – if you are lucky enough to have someone there (that 2nd person he mentioned!!) to get you out and call 911. I know from dealing with the explosion of an ammonia refrigeration system at food production plant – the entire town had to be evacuated and many were hospitalized.

  2. The air purifiers you mention are just ionizers that release negative ions into the air that electrically charge dust/odor particles in the air, & when charged, they drop to the floor as they become heavier than air. You can literally see the light film of charged particles that collect on the floor or horizontal surfaces We’ve used one in our rv for years. It very effectively eliminates the bathroom odors. They can be bought on Amazon for far less than on your link. We buy them for around $30. they do have a limited life span, probably a year or so.

    • I have not done the procedure for quite some time however, I know of several dealers that used it on models that were over 8 years old so I would believe it would be good. I have not used the air purifier yet, but dozens of people at the Hershey show commented how wonderful the product was.


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