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Health and Safety Executive / Local Authorities Enforcement Liaison Committee (HELA)

Local Authority Circular

  • Subject: Hazardous Substances
  • Open Government Status: Open
  • LAC Number: 37/9
  • Keywords: Urea Formaldehyde / Construction
  • Revised: September 2000
  • Review date: December 2000

To: Directors of Environmental Health/ Chief Environmental Health Officers of London, Metropolitan, District and Unitary Authorities and Chief Executives of County Councils.

For the attention of: Environmental Services / Trading Standards / Fire Authorities / Other

This circular gives advice to local authority enforcement officers



1 This circular gives guidance on the possible health risks arising from the use of urea formaldehyde foam as cavity wall insulation in buildings. The circular takes account of recent research concerning the effects of exposure to formaldehyde and it is intended to assist local authorities in their role as enforcing authorities under the Health and Safety at Work etc Act 1974. However, it is important also to note that local authorities have responsibilities under the Building Regulations in relation to urea formaldehyde foam insulation (UFFI), in addition to enforcement of the Health and Safety at Work etc Act 1974. The policy lead with respect to the insulation of buildings lies with the Department of the Environment. The latest evidence tends to indicate that UFFI is not a significant hazard to health when it is installed in compliance with Building Regulations and to British Standard requirements.


2 In premises where the main activity is one for which the local authority is responsible, LA enforcement officers may be involved when persons in the premises are affected after the insulation work is completed. It should be noted that under Section 3(1) of the Health and Safety at Work etc Act 1974 that the duty of an insulation contractor extends only to the health and safety of persons affected by the conduct of an undertaking and not to their welfare. It is also considered that this duty only extends for a relatively short period after the work has been completed.

3 Various materials are available for filling the cavity walls of buildings to provide insulation, but the most widely used is urea formaldehyde foam (UFFI) insulation. Although over one million dwellings and many non-residential buildings have been insulated with UFF in the U K, only a small proportion of the buildings treated have given rise to complaints about health effects. These effects have been attributed to the release of formaldehyde and some local authorities have suspended the use of UFF as a result. There have also been suggestions that dust particles or other emissions from the foam might cause problems, although chemical and medical investigations have failed to confirm these points.

4 UFF insulation of buildings has been banned in Canada following complaints about emission of formaldehyde fumes into the occupied areas of buildings. A ban imposed in the USA was overturned by the United States Court of Appeals. Many of the problems in North America appear to have arisen in timber frame buildings with wide cavities which would be regarded as unsuitable for UFF insulation in the U K and which fall outside the scope of the British Standard Code of Practice for foam insulation (BS 5618).


5 Formaldehyde vapour is irritant to the eyes and upper respiratory tract. Acclimatisation that is acquired is rapidly lost when exposure ceases. Formaldehyde vapour or dilute solutions are irritant to the skin. Skin sensitisation and allergic contact dermatitis can occur following exposure but these reactions are not likely at the gaseous formaldehyde levels which may arise in UFF insulated dwellings.

6 Animal studies have demonstrated that prolonged exposure to high levels of formaldehyde in some species of rodents, producing severe nasal irritation, result in tumour formation in the irritated region. HSE accepts that formaldehyde should be regarded as a proven carcinogen in rats under certain conditions of high exposure. However there is no epidemiological evidence to suggest that exposure to formaldehyde has produced cancer in humans.

7 For occupational exposure the current Recommended Limit is 2ppm 8 hour time weighted average concentration with a short term exposure limit of 2ppm 10 minute time weighted average concentration. An explanation of new occupational exposure limits is set out in the HSE Guidance Note EH40 "Occupational Exposure Limits 1984". The Health and Safety Commission Advisory Committee on Toxic Substances (ACTS) is currently considering a Control Limit for occupational exposure in the UK. Non-occupational exposure should be controlled to well within the 2ppm Recommended Limit since persons exposed in the population may include infant, old People and the sick. However, periods of exposure will vary widely and it is not possible to specify enforceable limits for non-occupational exposure.


8 There are many non-occupational sources of exposure to formaldehyde including the incomplete combustion of organic materials eg engine fuels, heating fuels, smoking materials and refuse burnt on bonfires. Formaldehyde is continuously present in the atmosphere in appreciable quantities (sometimes up to one-tenth the Recommended Occupational Exposure Limit in parts of central London). Smokers inhale peak concentrations of up to 40 ppm.

9 Exposure to formaldehyde can also arise from the curing or breakdown of formaldehyde-based resins, including those used for the treatment of fabrics to give crease-, soil-, or flame-resistant finishes and the use of particleboard eg wood chipboard, in furniture and building construction.


10 The Department of Environment has made Building Regulations to prohibit the use of UFF in unsuitable buildings and to control its installation elsewhere. Broadly the regulations only permit UFF insulation between cavity walls with masonry inner and outer leaves. The inner leaf should afford good resistance to vapour penetration.

11 The properties of urea formaldehyde foam are covered by BS 5617:1978, and BS 5618:1978 described good practice to be followed during the installation of UFFI in masonry cavity walls. The Code of Practice BS 5618 is concerned with the rain resisting function of the cavity wall and precautions against blockage of flues and ingress of formaldehyde. It requires that a card be left with the occupier drawing attention to the possibility of formaldehyde irritation and suggests that it can be alleviated by opening windows. An amendment to BS 5618 (AMD 4130 of 30 November 1982) requires the UF foam installer to take whatever preventative measures are considered necessary to ensure that there is a continuous barrier between the injected foam and the occupiable parts of the building.

12 The British Standards Institution Quality Assurance Division maintains a register of approved UFF installers. There are two trade associations for UFF installers, the National Cavity Insulation Association and the Cavity Foam Bureau.


13 The foam is produced on-site by mixing an aqueous solution of resin, and a hardener-surfactant solution with compressed air in a gun. The resulting foam has the consistency of shaving cream and is injected through holes into the cavity where it hardens and dries. In completed buildings, injection is entirely from the exterior but in buildings under construction part of the process may be through the inner leaf of the wall prior to plastering.

14 If the insulation has been properly installed to BS 5618 in a suitable building, most of the formaldehyde escapes through the outer leaf. When the inner leaf also, is permeable, formaldehyde may penetrate to the interior of the building; the resultant concentration is dependent on the rate of permeation and the degree of ventilation. Vapour penetration problems can occur in the following circumstances;

(1 ) where the inner leaf of the cavity in inherently porous, eg exposed brickwork or blockwork in rooms;

(2) unsealed construction holes, voids or ducts for services and gaps for pipework;

(3) in those steel or concrete frames structures with wider cavities than more conventional housing and where vapour permeable plasterboard or insulation board has been used as an inner wall. Additionally the construction of such buildings may involve a break in the continuity of the inner leaf at intermediate floor level;

(4) gaps in the inner leaf of a cavity wall may allow the foam to penetrate during the installation of UFFI and for it to then accumulate in roof spaces, ceiling voids. behind baths etc.


15 The DoE Building Research Establishment is investigating formaldehyde levels in buildings where UFFI has been installed. The HSE has investigated the exposure of workers installing the foam and has measured formaldehyde levels in non-domestic buildings. The results indicate that workers installing foam from the outside, or from the interior in buildings under construction, are exposed to low levels of formaldehyde (less that 0.05 ppm)

16 Formaldehyde levels of 0.05 ppm are commonly found in occupied domestic premises, prior to installation of UFFI, due to emissions from textiles, furniture etc. In favourable circumstances the installation of UFFI may cause the level to increase over the first few weeks to no more than 0.15 ppm. In less favourable circumstances levels of 0.5-1ppm may be reached in a few days. Levels exceeding 5 ppm have been found in rooms with a combination of adverse features eg a small badly ventilated cloakroom with several small breaches of the inner leaf of the cavity to accommodate services. The levels of formaldehyde depend on the degree of ventilation and also on ambient temperature. Formaldehyde levels will be higher within the cavity, or enclosed spaces communicating with it eg ceiling voids or system-built structures.

17 Following the initial increase, formaldehyde levels tend to decrease over a few weeks after installation, subject to fluctuations corresponding to variations in weather conditions. Complaints of formaldehyde odour lasting for 2 weeks or more after the installation of foam, have been reported in about 0.1 % of cases monitored in survey conducted over a total period of 40 months by BSI Quality Assurance Division. All but 0.3% of reported incidences of formaldehyde odour were resolved within 8 weeks. Not all the complaints involved allegations of ill health.


18 Enforcement officers may receive enquiries about UFFI and if consulted prior to a proposed installation, they should advise that to minimise the risk of formaldehyde emissions, the occupier should ensure that:

(1) the contractor is competent and registered with the BSI;

(2) the treatment will be applied in accordance with British Standard specification 5617 and to British Standard Code of Practice 5618. (As amended AMD 4130, 30 November 1982);

(3) the buildings have been competently surveyed to ensure they are suitable to receive the treatment;

(4) both the inner and outer leaves of the external walls are of masonry construction and the inner leaf is continuous;

(5) the plastering of the inner leaf is in good condition and that all cracks and gaps around service pipes are sealed.

19 If formaldehyde penetrates a building after installation of UFFI the building should be ventilated to the maximum extent that is reasonable in the circumstances of its use, eg by opening windows. Experience has shown that ventilation in this way, quickly reduces formaldehyde levels. Ventilation should be continued until the problem is abated either by the natural decrease in emission with time or by remedial measures which may include.

(1) removal of any foam that has penetrated from the cavity through the inner leaf;

(2) seating any gaps or cracks in the inner leaf through which foam has penetrated, or which may provide a vapour passage;

(3) making walls less permeable eg by covering with vinyl-coated papers or with paint (paint is available with formaldehyde-absorbing properties developed for coating particle board);

(4) use of proprietary absorbent materials or devices which are available but likely to be of little benefit unless sited near an emission source. This should be regarded as a possible short term addition to the measures in (1) and. (2);

(5) injection of ammonia into the cavity, has proved effective in a number of cases of persistent high formaldehyde levels, although more than one treatment may be necessary. Ammonia gas injection may introduce an additional vapour problem in the short term and in the long term possible adverse effects on the foam.

20 For the time being whilst any insulation work is in progress the existing Recommended Limit of 2 ppm, is applied by HSE to reduce irritation and the possible risk of sensitisation. Employers are also being encouraged to keep exposure as far below the Recommended Limit as is reasonably practicable.

21 The installation of cavity foam insulation is considered on balance to be a building operation and enforceable by HSE within the terms of Regulation 4 of the Health and Safety (Enforcing Authority) Regulations 1977.


22 Further information on urea formaldehyde foam insulation and the health effects of formaldehyde can be found in the following publications, the first three are obtainable from HMSO:

(1) Building Research Establishment Digest 236: Cavity Wall Insulation

(2) Building Research Establishment Information Papers IP 25/82: Formaldehyde Vapour from Urea Formaldehyde Foam Insulation

(3) Health and Safety Executive Toxicity Review 2: Formaldehyde

(4) Health and Safety Executive paper: "Formaldehyde in Air', MDHS19 (Methods of the Determination of Hazardous Substances) March 1983 Price: £1 and obtainable from the HSE.



Formaldehyde from Urea Formaldehyde Foam

Urea Formaldehyde Foam does not normally come into contact with the body, and reports so far do not indicate that the foam itself has any effects on health. In certain conditions Urea Formaldehyde Foam in cavity walls emits small amounts of formaldehyde vapour which might enter a building and cause irritation of the upper respiratory tract and the eyes of occupants. A very small number of persons have also complained of vague, mild symptoms of general nature whilst working or living in rooms insulated in this way. Studies are being carried out to try and identify the cause of these symptoms.

The Chief Medical Officer has, in the past, advised that completed studies of the results of exposure to formaldehyde have not shown evidence of increased risk of cancer, changes in lung structure of permanent impairment of lung function in man; a small proportion of individuals experience temporary sensitivity reactions of skin and respiratory tract. Since this advice was given, 5 further studies of exposure to formaldehyde have been completed. The results of these and other related experimental work do not suggest that any change is required in the advice given in March 1982.

Reports of further studies are expected in 1983 and 1984 and advice will be reviewed again in the light of the assessment of the detailed results by the independent specialist committees.

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