NASUWT casework increasingly reflects concerns arising from mould in schools. This information contains important advice for members on this issue.


Mould is the visible growth of fungi. There are many different types of fungus that cause mould to appear. Mould only grows in areas of high moisture, so will thrive in wet/damp conditions, particularly where it is also warmth, making damp school buildings particularly suitable for fungal growth.

Moulds are plant-like organisms which do not require light to grow. They obtain nutrients through consuming dead matter such as paper, cardboard and wood.

Where mould occurs

For mould to grow there must be a source of moisture. In classrooms, this is likely to be through ingress of water (e.g. a leaking roof or window), a leaking pipe or poor ventilation. Rooms where high humidity and condensation are likely, such as cooking rooms, changing facilities (especially where showers are available) and toilets are particularly susceptible to mould attack. Mould can also be caused by defects that lead to rising damp.

Signs of mould

Mould usually appears as a grey-black woolly growth on walls and ceilings. However, it is possible for mould to be hidden behind furniture and in wall/ceiling voids. The stuffy, musty smell which is usually associated with damp is normally due to the growth of mould somewhere in the room. Investigations should take place in order to ascertain the origin of the smell.

Problems caused by mould

Moulds spread by the release of spores into the atmosphere. These are considered allergens and have the potential to trigger allergic responses such as hayfever or asthma attacks in susceptible people.

Exposure to spores has also been linked to the development of upper respiratory tract symptoms such as coughs and wheezing in otherwise healthy people. There is also a potential link between the development of asthma in children and early mould exposure.

Some mould spores are also toxic and can lead to a suppressed immune system, particularly in the respiratory tract, and a consequential increase in chest infections.

Immunosuppressed individuals are particularly at risk of chest infections caused by mould exposure, as several types of mould are opportunistic human pathogens. In addition, some people have reported health effects such as fatigue, headache and difficulties in concentration, possibly due to the neurotoxic properties of some moulds.

There is some evidence that the odour produced by mould can also act as an irritant. Unpleasant odours can also cause stress responses such as headache and nausea.

Dealing with mould

Even brief exposure to mould spores can produce severe allergic effects in susceptible people. Therefore, mould must be dealt with seriously and with urgency.

  • When mould is discovered or suspected, the area involved should be isolated. In cases of extensive mould growth, a risk assessment should be carried out and it may be necessary to relocate teachers and pupils until the growth has been dealt with.

  • Even a small amount of mould should be reported without delay, as this may indicate a more substantial hidden growth and/or a developing problem. Investigations should take place to determine the extent and cause of the mould. There is no need to determine the type of mould present, as the process for dealing with the mould is the same, regardless of the type.

  • When the extent and cause of the mould has been determined, it should be cleaned by maintenance staff using appropriate cleaning materials, having first conducted a risk assessment, and the area treated to prevent regrowth. The cause of the growth must be identified, as regrowth will occur unless this is dealt with. Areas should not be occupied whilst mould removal is being undertaken.

    • The mould should not be disturbed or brushed or vacuumed away, as this will release further spores into the atmosphere.

    • Removing mould is not a job that teachers should undertake.

  • The cause may be straightforward, such as a leaking roof or pipe, and in these cases, rectification should also be straightforward. Where the mould is caused by lack of ventilation and/or high humidity, a combination of extractor fans, dehumidifiers and air conditioning units will be appropriate.

  • Mould growth is likely after a flood. Therefore, all items capable of soaking up water, such as carpets and upholstery, should be removed and replaced.

  • If the mould is found to be caused by rising damp, investigations should take place to determine the cause of the damp and a suitable solution enacted.

When mould is present/suspected, members should:

  • report the situation, using the normal reporting pathway in your school;

  • inform the NASUWT Health and Safety Representative;

  • if the mould is extensive and/or an odour of mould exists, request relocation to a different classroom while the problem is addressed. If your school refuses, contact the NASUWT immediately;

  • keep a record of the event;

  • if you are/have been working in an area with mould growth, see your doctor for a check-up and to log your exposure;

  • if your school does not deal with the issue, or if you require further advice, contact the NASUWT.