By Bill Weigand, Gary Loiben, and Gary Funari

Various sources release odors including new building materials, decomposing organic matter, incomplete combustion, and many others. Source identification and source location are the first steps in odor removal. In some cases, identifying the odor problem is easy because the odor is recognizable and the source is easy to find. In other situations, the odor will be unrecognizable and the source of the odor hidden and unknown.

Odor sources

A variety of tools are utilized to locate or detect odor sources. Air samplers (devices which draw measured amounts of air over tubes that react) can be used to confirm the absence or presence of specific gases. A portable electronic nose has been developed. Luminol is used by crime scene investigators to locate blood. Specialized ultraviolet lights are useful in locating some urine deposits. Many restorers use a moisture sensor to assist in finding odors because moisture and odors often go hand in hand. For practical purposes, your nose is still your best odor-locating tool!

Source removal

Source removal (to the extent possible) is the first step in a successful odor removal procedure. After identifying the source of an odor, the more of that source you can remove, the less of an odor problem you will have to handle. In pet odor situations, for instance, disposal of contaminated carpet padding and pretreatment of affected textiles with an acid rinse will dramatically improve your results. Keep in mind that if the project involves fire or trauma cleanup, make sure you have been given permission to remove items prior to starting the project.

Treat it

The second step in odor removal involves treatment of the residual odors after the sources have been removed. There are several options for treatment available including adsorbents, neutralization, oxidization, biocides, counteraction, masking, and bioenzymatic digestion.

Adsorbents, typically solid materials, such as activated charcoal or baking soda, capture and hold odors on their surfaces. Activated charcoal or carbon has been treated with heat and steam. Activated carbon works the same way as the box of baking soda you put in your refrigerator to adsorb odors: Odor molecules adhere to the surface of the sodium bicarbonate particles that make up baking soda.

Air cleaners equipped with activated carbon filters can be utilized to literally grab odorous gases out of the air. Specialty adsorbents are available with affinity to adsorb specific gases.

Neutralization implies a chemical balance or a mathematical equation where 1-1=0. Neutralization processes work well against chemical odors such as chlorine and various types of acids. For instance, the application of a solution of sodium bicarbonate and water will effectively neutralize the odor liberated from an acid spill. Sodium thiosulfate (also known as “photographer’s hypo”) neutralizes halogens such as chlorine, bromine, and iodine.

Oxidation, simply put, is a chemical reaction in which oxygen combines with another substance. Adding oxygen to odorous organic matter can be an effective odor control technique. Oxidizing agents like hydrogen peroxide and household chlorine bleach are effective deodorizers due to their oxidizing capabilities. Similarly, an ozone machine (an electrically
powered device used to produce an oxidizing gas) can be very effective in eliminating odor problems such as those caused by organic decomposition and by skunks.

Biocides are materials that inhibit or kill the growth of microorganisms. Some microorganisms produce odors due to chemical processes in which they participate, such as fermentation and decomposition. Disinfectants and antimicrobials are biocides which are effective in eliminating microbial-related odor problems. Odors caused by the metabolic process of microorganisms are commonly referred to as microbial volatile organic compounds or MVOCs. Serious microbial contamination should be properly remediated. These procedures are beyond the scope of this discussion.

Counteraction means to “work against.” Some odors are made up of a mixture of many compounds and as such are called complex odors. Complex odors, such as smoke odor, respond well to a series of odor-counteraction procedures such as suppression spraying, vapor phase re-odorization, and thermal fogging. Most odor-control products contain a combination of masking and pairing agents. Pairing agents combine with and change the perception of malodorous substances into odorless compounds.

Restoration odor removal

Masking is the disguising of a malodor with a stronger, more pleasant odor. These deodorants are masking agents. Time release deodorants can be granular, oils, or gels that have been saturated with deodorants. These products are designed to release the fragrance slowly over time.

Bioenzymatic digestion is a process whereby specially engineered bacteria produce enzymes that consume or digest odorous material such as animal excreta, spilled fuel oil, and decaying protein (spoiled milk, rotten fish/eggs). Bioenzymatic digestion is also used in laundry and in other cleaning processes including carpet cleaning.

Some odor problems can be remedied with just one of the techniques discussed above. Others require multiple procedures. Because of the introduction in recent years of improved odor-control products and application equipment, the industry’s capability for successfully solving odor problems is improving daily, and solving odor problems is becoming much easier and more profitable.


Bill Weigand has been in the cleaning and restoration industry since 1980 and helped develop many odor-control products and techniques that have become industry standards. He instructs both RIA and IICRC classes.

Gary Funari has spent 33 years as a construction specialist and holds multiple certifications. He is a restoration and insurance RSA instructor in fire and water damage restoration and microbial damage remediation and odor control.

Gary Loiben is a 30-year veteran of the cleaning and restoration industry. He has trained thousands in the industry in fire, odor, and water damage restoration. He holds industry certifications and is a training instructor for RSA.

Weigand, Funari, and Loiben can be reached at techquestion@RSA-HQ.com.