Spray foam fumes and health: what is known

HSE's health guidance concerns the spraying stage: it treats spraying isocyanate products as a significant cause of occupational asthma, and covers sprayers and anyone present until the area clears^[1]. Spray foam is made on site from two liquid components that react together, one of which contains isocyanates (MDI)^[4][2].

• Protection for sprayers: HSE guidance calls for constant-flow air-fed breathing apparatus, kept on until the sprayer is out of the spray area, plus keeping other people away and health checks for workers^[1].
• Protecting the household: one product approval requires the loft hatch closed and water tank covers on until vapours clear, and ventilation of lower floors because MDI vapour is heavier than air^[2].

The industry Code of Practice adds that spraying indoors at high pressure needs a full-face or hood respirator supplied with fresh air^[4]. In the US, the EPA lists isocyanate vapour and spray mist during spraying and curing as the recognised exposures^[3].

The industry Code of Practice says UK REACH has required training for anyone using pMDI since August 2023^[4]. A matching EU rule, Commission Regulation (EU) 2020/1149, requires training from 24 August 2023, renewed at least every five years, unless the product contains less than 0.1% diisocyanates; its legislation.gov.uk text carries a UK extent marker^[5].

The same Code says only installers trained and approved by the manufacturer should apply the products, with trainees working only under a trained installer's supervision^[4]. Product approvals also limit installation to installers trained and approved by the approval holder^[6]. Before work starts, ask the installer for evidence of both. See how spray foam should be installed.

No re-occupancy time set by a UK regulator was found for this guide: HSE's spraying guidance covers workers and others present until the area clears, not when a household can return^[1]. The figures in circulation come from an industry code, product approvals and US agencies.

The Code also says the foam reaches 90% cure within an hour, with full cure taking a further 23–72 h depending on temperature^[4]. Ask your installer, before work starts, what time the documents for your product give and how the space will be ventilated.

One UK product approval does not treat cured spray foam as a health hazard, but the evidence on longer-term emissions is limited^[2][3].

• BBA product approval 11/4816 says the cured product is not considered a health hazard^[2].
• A 2020 article in the RICS Built Environment Journal says off-gassing is usually temporary^[9].
• In the US, the EPA describes fully cured foam as relatively inert, but says the potential for off-gassing is not fully understood and more research is needed on curing and re-entry times^[3].

Cutting, grinding or heating cured foam is different: the US EPA lists dust and fumes from doing so as a recognised exposure^[3]. Don't cut or strip foam yourself to deal with a smell; see should you remove spray foam?.

In the US, persistent smells are reported, but there is little research, and no UK study of smells or symptoms was found for this guide^[8][10].

A small US study published in 2014 looked at 13 adults in 10 homes where spray foam had been improperly retrofitted^[10]. All reported a fishy odour; improper mixing and inadequate ventilation featured in some cases; people reported symptoms affecting the eyes, nose and airways, among others; and in those homes VOC levels (volatile organic compounds in the air) fell after the foam was removed^[10].

Because it studied only homes already known to have problem installations, that study cannot tell you how common smells or symptoms are. A US consumer safety sheet notes that persistent odours are reported but gives no cause^[8].

Ventilate, contact the installer, and speak to your GP if you have symptoms. This page cannot tell you what is causing a smell or whether it affects anyone's health.

1. Ventilate. Open windows and keep the home well aired, and avoid spending time in the loft until the foam has been looked at.
2. Write it down. Note when you first noticed the smell, where it is strongest, and whether it changes with warm weather or heating. Take dated photos of the foam if you can see it safely from the hatch.
3. Contact the installer in writing. Ask which product and batch were used and ask them to inspect. The industry Code of Practice expects both details in the homeowner pack, with a short version left in the loft^[4].
4. If the installer has gone or won't respond, the same Code expects installers to send a copy of the homeowner pack to the manufacturer, so the manufacturer named in your paperwork may hold a record^[4].
5. Speak to your GP if you or anyone in the home has symptoms you are worried about, and mention the foam and when it was installed.
6. Get consumer advice if it stalls. The Citizens Advice consumer helpline is 0808 223 1133 (Welsh 0808 223 1144; numbers as at October 2026), and its advisers can pass complaint details to Trading Standards^[11]. See your consumer rights.

More are on spray foam claims we checked.