Does spray foam insulation off-gas and is it safe for my family in Saint John NB? | Insulation IQ?

Question

New Brunswick Insulation · Accepted Answer

This is a legitimate health and safety question that deserves a thorough, honest answer rather than a blanket reassurance. The short version is that properly installed, fully cured spray foam is considered safe for residential occupancy — but the curing period and installation process do present real chemical exposure risks that require strict protocols, and there have been documented cases of persistent off-gassing when installation goes wrong.

What is in spray foam, and what off-gasses? Two-component polyurethane spray foam is made by combining an A-side (typically polymeric methylene diphenyl diisocyanate, or pMDI) with a B-side (a polyol blend including catalysts, blowing agents, and flame retardants). During the active spray and curing phase, the uncured chemicals — particularly the isocyanates on the A-side — are significant respiratory and skin sensitisers. Isocyanate exposure is a leading occupational cause of chemical-induced asthma and is classified as a probable human carcinogen by some regulatory bodies at high exposure levels. This is why professional spray foam applicators wear full-face supplied-air respirators and protective suits during application — standard dust masks or N95 respirators provide no meaningful protection against isocyanate vapours.

The occupant re-entry period is critical. Industry guidelines and Health Canada guidance generally recommend that occupants — particularly children, pregnant women, and anyone with respiratory sensitivities — stay out of the treated area for a minimum of 24 hours after application, and many contractors recommend 24–72 hours for the building as a whole if the work was done in an enclosed space with limited ventilation. During this window, volatile compounds from the reaction are actively off-gassing. Adequate mechanical ventilation — opening windows and running fans to purge the space — is essential during and after application.

Once fully cured, spray foam is chemically inert. The A and B components have reacted completely, the isocyanates are locked into the polymer matrix, and the cured foam does not continue to release meaningful quantities of harmful compounds. This is the normal end-state for a correctly installed product, and it is the basis for the safe for occupancy claims made by manufacturers. Independent air quality testing of homes with properly installed, fully cured spray foam has generally not found elevated levels of concerning compounds.

The problem cases — and they are real — occur when the foam is installed off-ratio. If the proportioner is delivering the A and B sides in incorrect proportions (due to equipment malfunction, clogged tips, temperature issues, or operator error), one component will be present in excess of what the other can react with. Excess unreacted B-side polyols, amine catalysts, and flame retardants can off-gas from the foam for weeks, months, or even years after installation, producing odours and chemical exposures that have caused serious health problems for homeowners. This is not a theoretical risk — it led to a wave of complaints and investigations in the United States in the 2010s and prompted the U.S. EPA to issue guidance on spray foam off-gassing. Canadian regulatory oversight is similar in structure but enforcement is largely provincial.

For Saint John families specifically, the off-ratio risk is the main concern, and it comes down entirely to contractor quality and equipment maintenance. A well-maintained proportioner running at correct temperatures with fresh, properly stored chemicals will deliver an on-ratio mix. A contractor whose equipment has not been serviced, whose chemical drums have been stored in cold conditions (a real risk given Saint John's winters), or who is cutting corners on technique is more likely to produce off-ratio foam.

Signs of problematic foam include a persistent fishy, amine, or chemical smell that does not dissipate after 72 hours, foam that appears soft, tacky, or greasy after curing, or foam that has an uneven, frothy, or discoloured appearance. If you notice any of these, do not re-occupy the space without air quality testing and contact the installer immediately.

Intumescent paint and fire code compliance are separate but related safety issues. The NB Building Code requires that spray foam exposed in occupied or habitable spaces be covered with a thermal barrier — typically 12.7 mm (half-inch) drywall — to limit flame spread. Exposed foam in an unfinished basement is not compliant and should be covered.

Practical advice for Saint John homeowners: Ask your contractor for product data sheets and the manufacturer's re-entry time recommendation. Arrange to be away from home during application and for at least 24–48 hours after. Ventilate aggressively. If any unusual smell persists after 72–96 hours, escalate immediately rather than waiting.

The New Brunswick Insulation network features contractors who are experienced with New Brunswick's regulatory requirement

Ready to Start Your Insulation Project?

Related Questions