Mould Spore Exposure & COSHH: What Your RAMS Must Include Before Starting Remediation Works

Table of Contents

• Mould as a Biological Agent Under COSHH
• COSHH Assessment Requirements for Mould Work
• Health Effects of Mould Spore Exposure
• RPE Selection: What Level is Needed?
• Control Measures in Mould Remediation RAMS
• What Your RAMS Must Include
• Frequently Asked Questions
• Next Steps

Mould as a Biological Agent Under COSHH

The Control of Substances Hazardous to Health Regulations 2002 (COSHH) apply not only to chemicals and dusts but also to biological agents — microorganisms including bacteria, viruses, and fungi (moulds). When mould growth is disturbed during remediation works, large quantities of fungal spores are released into the air. These spores are biological hazards under COSHH, and their management must be addressed in your RAMS and COSHH assessment before work begins.

Under Regulation 7 of COSHH, employers must prevent or adequately control exposure to hazardous substances. For mould spores, the practical control hierarchy is:

1. Elimination — Remove and dispose of heavily contaminated materials (not always possible)
2. Containment — Prevent spore spread using negative pressure and physical barriers
3. Suppression — Wet methods to reduce spore generation during physical removal
4. RPE — Respiratory protective equipment as the last line of defence

RPE alone is not an adequate control for mould remediation. Your RAMS must demonstrate that containment and suppression measures are in place before RPE is specified.

Browse all trade RAMS templates on the RAMS AI trade hub — covering 22 specialist construction trades.

COSHH Assessment Requirements for Mould Work

A COSHH assessment for mould remediation must address:

• Nature of the biological agent — Identify the type of mould where known (common types include Cladosporium, Aspergillus, Stachybotrys). Note that the species of mould affects the health risk profile. Stachybotrys (black mould) is associated with more serious health effects than common surface moulds. If the mould species is unknown, treat it conservatively.
• Scale of the infestation — The area of mould growth affects the quantity of spores generated during disturbance. Extensive mould growth (>1 m²) is typically treated as high risk and requires full containment, negative pressure, and appropriate RPE.
• Routes of exposure — Inhalation (primary), skin contact, and eye contact. The COSHH assessment should address all relevant routes.
• Vulnerability of operatives — Operatives who are immunosuppressed, have asthma, or are known to have fungal allergies are at significantly greater risk. Pre-placement health screening should be considered for high-exposure mould remediation roles.
• Control measures — Containment, negative pressure, wet methods, HEPA vacuuming, decontamination, RPE, and PPE.
• Exposure monitoring — For extensive mould remediation projects, air sampling before, during, and after remediation provides evidence that controls are working. While not always mandatory, it is increasingly expected on larger projects.
• Health surveillance — Consider whether a health surveillance programme (baseline respiratory questionnaire, periodic review) is appropriate for operatives regularly carrying out mould remediation work.

Health Effects of Mould Spore Exposure

Your COSHH assessment and RAMS should acknowledge the health effects associated with mould spore inhalation. These include:

• Allergic reactions — Hay fever type symptoms (rhinitis, conjunctivitis) are common in sensitised individuals.
• Asthma — Mould spore exposure can trigger asthma attacks in existing asthmatics and, with repeated high-level exposure, may cause occupational asthma in previously healthy individuals.
• Hypersensitivity pneumonitis (HP) — Also known as extrinsic allergic alveolitis, HP is a serious lung condition caused by repeated inhalation of organic dusts including fungal spores. It can cause permanent lung damage if not identified early.
• Opportunistic infections — In immunosuppressed individuals, some mould species (particularly Aspergillus) can cause invasive infections. Immunosuppressed persons should not carry out mould remediation work.
• Mycotoxin exposure — Some moulds produce mycotoxins (particularly Stachybotrys) that may cause additional health effects beyond those from spore inhalation alone.

The HSE publication Biological agents: Managing the risks in laboratories and healthcare premises provides additional guidance on biological hazard assessment.

RPE Selection: What Level is Needed?

Respiratory protective equipment for mould remediation must be selected based on the specific activity and mould scale. The HSE's RPE selection guidance requires that the RPE selected provides an adequate assigned protection factor (APF) for the expected exposure level.

• Surface cleaning and HEPA vacuuming of minor mould (<0.5 m²) — FFP2 disposable filtering facepiece may be adequate if containment measures are in place.
• Remediation of moderate to extensive mould (>0.5 m²) — FFP3 disposable filtering facepiece minimum. Powered air purifying respirators (PAPRs) with HEPA filter provide greater protection and comfort for extended work periods.
• Spray application of biocides — The RPE class depends on the biocide product. Consult the product COSHH assessment. Some spray products require half-face respirator with appropriate filter cartridges, or air-fed RPE.

All RPE must be face-fit tested for each wearer to ensure an adequate seal. Records of face-fit testing must be maintained. Operatives with facial hair that prevents an adequate seal must use hood-type powered air purifying respirators (PAPRs).

Control Measures in Mould Remediation RAMS

Your RAMS method statement should specify the full hierarchy of controls:

• Isolation — Seal the work area with polythene sheeting. Close all ventilation openings. Place adhesive notice on access points.
• Negative pressure — Set up a HEPA-filtered negative air pressure unit to maintain negative pressure within the work area. This prevents spores from migrating to adjacent areas.
• Wet methods — Mist mould surfaces with dilute biocide before any physical removal. This reduces spore generation during scraping and brushing by keeping spores wet and heavy.
• HEPA vacuuming — Vacuum all loose spores and dust before and after physical removal. Only HEPA-filtered vacuums are permitted — standard vacuums spread spores.
• Physical removal — Remove loose mould growth and, where necessary, contaminated substrate materials. Double-bag all waste before removing from the work area.
• Biocide application — Apply treatment product in accordance with the COSHH assessment and manufacturer's instructions.
• Drying and ventilation — Allow adequate drying time and ventilation before other trades enter.
• Decontamination — All operatives must decontaminate before leaving the work area: remove disposable coveralls, wipe footwear, remove RPE last.

For more detail on RAMS structure for mould remediation, see our guide on Mould Remediation RAMS: A Practical Guide for Contractors.

What Your RAMS Must Include

Before starting any mould remediation work, your RAMS and supporting documentation should include:

• COSHH assessment for mould spore exposure
• COSHH assessment for each biocidal product to be used
• RPE specification for each task with face-fit test records for all operatives
• Containment and negative pressure plan
• Wet methods procedure
• Waste management plan (classification and disposal route for contaminated materials)
• Decontamination procedure for operatives
• Health surveillance arrangements for regular mould remediation operatives
• Emergency procedures for spill, fire, or operative becoming unwell
• Supervisor and operative sign-off confirming briefing

Frequently Asked Questions

Q: What is the legal exposure limit for mould spores?
A: There is currently no UK Workplace Exposure Limit (WEL) for mould spores specifically. The COSHH duty is to reduce exposure to the lowest reasonably practicable level. Guidance from the HSE and professional bodies suggests that visible mould disturbance without adequate controls carries significant risk.

Q: Do we need face-fit testing for disposable FFP3 masks?
A: Yes. All tight-fitting RPE including disposable filtering facepieces must be face-fit tested for each individual wearer. HSE guidance is clear that a mask that does not seal to the face provides little protection. Records of face-fit testing must be kept and made available on request.

Q: Can we use a standard vacuum cleaner during mould remediation?
A: No. Standard vacuum cleaners pass fine particles through their filters and back into the air. Only HEPA-filtered industrial vacuum cleaners may be used during mould remediation works. HEPA filtration to at least Class H (99.995% efficiency at 0.3 microns) is required.

Next Steps

Generate a COSHH and CDM 2015 compliant RAMS for mould remediation works using the Mould Remediation RAMS generator on RAMS AI.