Is Spray Foam Toxic Once Cured?

The two stages: spraying and cured

Spray foam is produced on site by combining two liquid components that react and expand within seconds. One contains isocyanates, a family of compounds known to cause breathing problems and skin reactions, and the other is a resin blend with catalysts, blowing agents and often flame retardants. While the foam is going on and curing, vapour and fine droplets are in the air. Installers wear respirators and protective suits for this reason, and the house or the work area is normally vacated and ventilated for a period afterwards. The product manufacturer sets that period, and the data sheet should state it.

After curing, the reaction has finished, and the foam is a solid plastic with the reactive chemicals consumed. In that state it is generally regarded as inert and does not off-gas in a way that harms the occupants. That is the picture when everything has gone to plan, which is the key condition.

When cured foam still causes trouble

Foam that has not cured properly is the problem. If the two components were mixed in the wrong ratio, the temperature was wrong, or the substrate was damp, parts of the foam can stay tacky or give off a persistent fishy or chemical odour. Some households have reported headaches, irritation or breathing difficulties linked to that, and complaints are the usual reason people ask this question. If you can smell a strong chemical odour weeks or months after the work, tell your installer and your doctor, and do not just live with it.

Loft foam can also affect indoor air indirectly. Any gaps between the loft and the living rooms allow air, and with it any odour or dust, to pass down. That is another reason to get the airtightness right at the hatch and around fittings. If there is mould too, that is a separate health issue, covered in our page on spray foam insulation problems.

Burning, cutting and removal

Foam changes the risk if it is heated or disturbed. Cutting and scraping cured foam creates dust and fine particles that you should not breathe, and burning it releases dense smoke and harmful gases, so the material should never be burned or heated with a torch. That is a reason not to remove foam yourself. The work needs masks suited to dust, eye protection, gloves and ventilation, and the waste has to be bagged and disposed of properly, not left in a corner of the garden.

When we remove foam, we protect the house, cut and lift the material by hand tools, bag it and take it off site, and clear up when finished. The steps are set out on our page about spray foam removal. If foam has been in a fire, or has been overheated, tell us before we begin, because the residue may need extra care.

Children, older people and anyone with asthma or allergies are more sensitive to irritants, so if a household member has symptoms that began after the foam went in, take that seriously and mention the timing to your doctor. Keep the product name, batch details and installer contact on file, because they help when a medical or consumer complaint needs evidence, and photograph any tacky or discoloured patches with the date. Ventilating the house and keeping the loft hatch closed reduce exposure in the meantime.

Disposal is a point people forget, and a poor one to leave to chance. Offcuts and removed foam should not go in the household bin in large quantities or be burned. The waste carrier should be able to say where it goes, and we deal with this as part of any removal.

What you can do now

Start with the simple checks, since they cost nothing and need no ladder beyond the hatch.

Check the paperwork for the product name and the safety data sheet, which lists the hazards and the re-entry time after application. Look at the foam for tackiness, a sticky surface or yellowing, and note any smell. Keep the loft hatch closed and sealed, and ventilate rooms if a smell lingers. If anyone in the house is unwell and you suspect the foam, seek medical advice and ask the installer to investigate. We are roofers, not toxicologists, so we cannot diagnose health effects, but we can inspect the foam and the roof, photograph what we find and advise on removal if it is the sensible answer.

You can see how the paperwork should look on our spray foam paperwork page and the full service is on the spray foam hub.