A property manager in Delson, on the South Shore of the Montérégie region, contacted us after noticing repeated entries of mice in several units of a twelve-unit building. Despite occasional interventions over the years, the rodents inevitably returned in the autumn. The owner suspected flaws in the plumbing system and drain connections, but no traditional visual inspection had identified the specific access routes. Our technicians proposed a professional smoke test to map all the infiltration points before proceeding with the final sealing. This methodical approach avoids blind interventions and allows efforts to be focused where they are really needed.
Preparation and conduct of the smoke test
Before the intervention, the Nova Extermination team inspected each level of the building, from the basement to the attic, noting the areas where pipes were passed, the junctions between the walls and the floor, as well as the service entrances. On the morning of the test, technicians temporarily sealed the roof vent outlets to maintain the pressure needed for the inert smoke to spread throughout the drain and plumbing system. The smoke generator was connected to the building’s main cleaning manhole. In less than fifteen minutes, whitish plumes appeared in several unexpected places: along a cracked foundation wall, around the washer drain pipe on the third floor, and behind a kitchen cabinet on the ground floor. These results were photographed and recorded in a detailed report submitted to the manager at the end of the day.
The test also revealed an opening in the sealing sleeve of a ventilation column crossing the party wall between two dwellings. This type of defect is common in buildings built before the 1990s, a period when sealing standards were less stringent. Without the smoke test, this flaw would have remained undetectable by simple visual observation. The inert smoke used is made of non-toxic vegetable glycol and dissipates completely within a few hours without leaving any residue on the surfaces.
Sealing work and recommended corrections
Thanks to the precise mapping obtained during the test, our teams were able to intervene surgically. The foundation cracks were filled with hydraulic mortar and then covered with a rodent-resistant polyurethane sealant. The pipe sleeves were replaced with stainless steel models with a compressible seal, eliminating any gaps that could be gnawed or widened by mice. The caulking of the entry points was carried out at each partition penetration, paying particular attention to the ground floor dwellings that communicate directly with the utility spaces in the basement. All of this work was validated by a second smoke passage, which confirmed the complete tightness of the network.
For owners of rental properties in the Delson area and neighbouring municipalities such as Saint-Antoine or Prévost, a preventive smoke test every five to seven years is strongly recommended. The build-up of mineral deposits in drains, the degradation of joints and renovation work are all factors that create new breaches over time. Each renovation involving the opening of partitions or the addition of new pipes is an opportunity to check the overall tightness of the building before closing the walls. You can consult a similar example carried out on the South Shore in our previous smoke test.
Long-term follow-up and prevention
Once the work was completed, our extermination team in Delson implemented a quarterly monitoring program that included inspection visits to sealed areas, checking control traps placed around the perimeter of the building, and preventative maintenance of service lines. The manager now has a complete register of interventions, useful both for insurance management and for communication with tenants. The affected homes have not reported any new intrusions since the intervention. Rigorous monitoring combined with prior detection by smoke test is the best strategy to keep a rental property free of pests in the long term. Also check out our other commercial building smoke test case study to see how we adapt our approach depending on the type of property and the pests involved.