Smelly Intrusions


When a homeowner detects unpleasant odors shortly after a water intrusion, often their first thought is “Mold!” This may trigger further reactions up to and including, “It’s toxic. We’ll have to bulldoze the house and rebuild.”

We know this is an extreme overreaction, but we still need to deal with distraught clients.  Why do odors appear so suddenly and intensely following a water loss situation? Why is it sometimes hard to persuade a client that your efforts have successfully eliminated the odors?

Odor molecules are small to mid-sized molecules. Exactly how these molecules trigger the sensation of smell is not completely understood. One popular theory can be illustrated by a lock and key. Receptors (the locks) at the ends of our olfactory nerves are specially shaped. Only the right shaped molecule (the key) will fit into the receptor, activating the sensation of odor.

Even when odorous molecules may be present in a structure, there is no sensation of smell until the odor molecules reach our olfactory nerves. The odor must become volatile or evaporate and then circulate in the air and reach our noses. Water vapor is a favored transport method for odor molecules to ride from their starting location to our noses.

Thus the presence of moisture increases the perception of odor. For example, the smell of a wet dog is more pronounced and objectionable then the smell of a dry dog. The dog smelled the same before it got wet. The water does not add any odor, but combining water and the formerly dry dog produces the wet-dog smell that reaches our nose.

Potential odor sources are lurking throughout every building. There are no dogs under the carpet, but there are mold spores and likely dormant colonies of mold waiting for moisture to spring back to life.

But mold is far from being the only source or even the most common cause of odor triggered by water. There are countless types of bacteria and other microorganisms that trigger into cycles of growth and reproduction as soon as moisture is present. When they are active they will begin digesting any available food and off-gassing unpleasant odors. Old pet urine deposits, spilled food, and tracked-in grass, leaves or other organic material provide a banquet for the hungry bacteria.

To summarize, odors are more pronounced when water or high humidity is present for two reasons:

  1. Water vapor carries smells to the nerves that sense odor.
  2. Water spurs growth, reproduction and activity of microorganisms that produce odors.

How do we eliminate or reduce these odors? How do we assure that our customers are satisfied with the results?

First and foremost is to dry the wet materials and reduce the humidity in the air. This would be the priority for any water damage restoration, and it has the added advantage of reducing odors. When your drying plan permits, begin ventilation with fresh air. Move bad, stale odors out and bring in fresh air to dilute any remaining odor.

The key in any deodorization process is to remove the source of the odor. This may or may not be covered by the scope of work you are performing. Materials that are moldy or contaminated by Category 3 water will be removed and discarded. But carpet wet from a Category 1 water source may not be replaced, even if it does contain pre-existing urine contamination. You may have to negotiate with your client to perform additional services if they want 100 percent elimination of the odor.

Finish by applying a solution of an odor-absorbing/ encapsulating type of odor-control product to capture any remaining odor molecules.

In order to completely satisfy our clients, it may be necessary to remove both the real odor and the odors they only think they smell, known as “psychological odors.” Odor and memory are closely associated (see box). Removing the psychological odor depends, in large part, on instilling confidence in our client. Our professional manner, the tools we use, and our own confidence in our ability and training all play roles in assuring them we have completed the task thoroughly and correctly.

Receptors are concentrated in the epithelium, a thumbnail-sized area with about ten million sensory neurons. These receptors are so sensitive they can detect one odor molecule among millions in the air. On average, men can identify 3,000 to 5,000 distinct odors. Women can identify close to 10,000.

These nerve endings are the only nerves in our bodies that are replaced every few weeks. In addition, they have only a thin layer of mucus protecting them from stimuli in the environment. This is significantly different from nerve endings for our other sense, which are located under our skin, behind our eyeballs or inside the ears.

The other end of the nerves is housed in the olfactory region of our brains. Therefore, these nerves are truly where our brain meets the outside world. This might be why there is such a strong connection between odor and memory.

Odors can trigger memories. The reverse is also true — recalling a memory might include a strong sensation of odor. As with other aspects of odor, women are more sensitive. Seeing a stain where we previously smelled an odor might spark a recall of that odor. This psychological odor is not a real odor but your brain can’t tell the difference.

Scott Warrington has more than 40 years of experience in the carpet cleaning industry and related fields. He serves as the technical support specialist for Bridgepoint Systems and Interlink Supply. He can be contacted at [email protected].

Cleanfax Staff

Cleanfax provides cleaning and restoration professionals with information designed to help them manage and grow their businesses.

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