Mold or Mice: What on Earth Is that Smell?

Client:  “Good morning! I have this awful moldy smell coming from my garage, and it’s making my entire family sick. It seems to be spreading. Can you give us an estimate to remove the mold from our garage?”


We receive calls like this every day–homeowners noticing unpleasant musty odours and wondering if they’re caused by mold. It seems that they try everything possible, and yet, they still can’t get rid of that moldy smell.

It doesn’t matter how clean the rest of your home may be, a persistent odour can ruin the atmosphere in your home. As we talked to our client, Lauren, we learned that her husband’s boss was coming for dinner and Lauren was worried the unpleasant smell would leave a lasting bad impression.

mold or mice

Frustrated over these persistent odours and concerned about their health, they turn to us to tackle their dilemma.

For this particular client, we were able to schedule a same-day appointment and take a look (or smell!) of the problem for ourselves. When we stepped into their garage, the odour was undeniable. It was very strong, very unpleasant and very real.

We began our diagnostic odour inspection, which can even be done through a virtual inspection, using a particle scanner, moisture metre, and a thermal imaging camera. All of the diagnostics yielded normal indoor environmental conditions, and we able to quickly determine that the odour was not being caused by mold growth.

This conclusion was not easily accepted by our client, who was absolutely convinced that the odor was a result of mold growth. After all, they were all getting sick and had read that mold could cause these types of symptoms.

However, based on our extensive experience with mold, we explained to our client that the odour was more likely caused by mouse urine and fecal deposits. This odour, although similar to the common moldy smell, is very specific, and we have dealt with it countless times.

We also informed our client that rodent infestations in and around the home remain the primary risk for hantavirus exposure. Even healthy individuals are at risk for HPS (Hantavirus Pulmonary Syndrome), a severe, sometimes fatal, respiratory disease in humans.

What are the symptoms of HPS?
HPS begins as a “flu-like” illness. In the early www of the disease, you may have the following symptoms:

  • Fever
  • Sore muscles
  • Headaches
  • Nausea
  • Vomiting
  • Shortness of breath

In North America, mice and rats can act as reservoirs of the virus. The rodents shed the virus in their urine, droppings and saliva. The virus can be contracted by humans via airborne transmission. When fresh rodent urine, droppings or nesting materials are stirred up, tiny droplets containing the virus get into the air.

As a result, when we encounter an environment that may contain a rodent issue, we wear full-body safety gear and take every precaution necessary to ensure that he contamination does not spread.

How We Fixed It:
Although skeptical of our conclusion, our client decided to trust our expertise and allow us to perform a full remediation and disinfection of their garage.

Following the general IICRC guidelines, we created a containment unit within the garage, using negative pressure to expel any dust and debris caused by the removal of the drywall. After only a few feet of drywall were removed, we found the nest!

We removed ALL of the contaminated materials (insulation, drywall, non-structural studs, etc.) and thoroughly disinfected the remaining areas. We even found some openings that may have allowed the mice to make their way into the garage in the first place, and of course, sealed them properly.

Our client was amazed. Never would he have thought that mouse deposits could have been the culprit behind this odour issue.

All in all, this case study goes to show that odours associated with rodent infestations can be easily mistaken for those produced by mold and, likewise, can cause very serious reactions in occupants.

Thus, odour inspections, especially in regions like Ottawa, are crucial in determining the cause of the odour so you can act appropriately to remediate it. Call Mold Busters today for more information about our services, including our Montreal mold removal offerings.

John Ward

Resource info

Author: , Mold Busters
Published: August 10, 2018
Updated: April 12, 2019