Q&A OF THE WEEK: "How Can I Get Rid of the Smell of Rodents in an Old House?"

Posted on August 10th, 2023

Q: Do you know of any way to get rid of the smell of rats and mice? My daughter bought a house in an old neighbourhood and rodents have been living in the frame walls of the finished basement for years. The walls have been stripped but the smell is still strong.

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A: A small, portable electric appliance called an ozone generator is the industry standard for eliminating odours in professional restoration situations. Experts use this technology to get rid of the smell of smoke and mold and it’s very effective. I have an ozone generator at my place and it works really well.

Ozone is an unstable oxygen molecule made of three oxygen atoms instead of the usual two. This extra oxygen atom makes ozone a powerful oxidizer, chemically breaking down the odour-causing compounds. Ozone generators convert oxygen from the air into ozone using electricity. In your daughter’s case, the odour-causing compounds would mostly be from the urine of rats and mice. This odour is quite durable but ozone is up to the job. I’ve seen it work well.

Expect to pay at least a couple of hundred dollars for an effective ozone generator, and look for a model rated to handle the square footage of area involved. I use my ozone generator periodically around houses and even in vehicles. That’s my unit you see below. It keeps everything quite odour-free. Click here for my suggestion for a newer and better model.

This is my ozone generator and it uses a special light bulb to convert oxygen in the air (O2) into ozone molecules (O3). I’ve used this unit for many years to deordorize rooms and vehicles. O3 doesn’t mask odours, it breaks down the compounds that cause them.

Ozone treatments do need to be done with safety in mind so follow the instruction manual of any machine you buy. That said, it’s easy to be safe when you realize that ozone breaks down quite quickly after the generator shuts off. Although high concentrations in the air can be irritating, after less than an hour ozone disappears in a room. Simply close the door where the generator is working, but powered by an extension cord outside the room. Unplug the cord and let the room (or vehicle) remain closed for a while. When you open the door you’ll be amazed at how nice and fresh everything smells.

Wet Basement Check

When it comes time to refinish the basement, don’t get in a hurry. Ideally your daughter should observe the basement for at least a year to make sure there are no water leaks. It sounds like she has an older home, and these are more likely to have basement leaks during wet weather than in more modern homes. Even the tiniest bit of water inside a finished wall or floor can cause big mold growth.

Also, I always recommend against any kind of fiber-based insulation in basements. There are many ways big mistakes can be made when finishing a basement, and many of these mistakes are currently made all the time even today. Never finish a basement without completing a planned moisture audit of the space. The video below is from my course FINISH YOUR BASEMENT THE RIGHT WAY. It outlines how traditional basement waterproofing systems work. Your daughter may need to understand this depending on what she finds moisture-wise. There are many ways basements are currently being finished badly, promoting mold in the process.

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