Biological Contamination in Offshore Wind Turbines: The Hidden Hazard

Offshore wind is no longer a small experimental sector. The GWEC Global Offshore Wind Report 2025 put global offshore wind capacity at 83.2 GW by the end of 2024, with 8 GW connected in 2024 alone, and forecasts another 350 GW added between 2025 and 2034.

That growth changes the maintenance conversation. A biological-contamination problem inside one turbine is a site task. The same problem repeated across a fleet becomes a worker-exposure issue, an O&M time issue and a documentation issue. The earlier a team defines the risk, the easier it is to control without turning every visit into a reactive clean-up.

In a turbine interior, biological contamination can include visible mould, mildew, biofilm, damp organic residue and odour linked to microbial growth. Not every stain is biological. Not every biological finding is a severe health risk. But it should not be ignored simply because the surface is inside an engineering asset rather than a building.

HSE guidance on biological agents at work describes biological agents as micro-organisms that may cause infection, allergy, toxicity or another hazard to human health, and notes that people can encounter biological agents because of the environment they work in. That matters for turbine interiors because technicians may be exposed by contact, inhalation or disturbed residue during cleaning and maintenance.

Offshore turbine interiors are not open, dry workshops. Towers, nacelles, hubs and transition pieces can see damp air, salt, limited ventilation, temperature change, technician traffic and long gaps between visits. Even where the asset is designed to protect key systems, interior surfaces can still create local conditions where damp residue persists.

Industry humidity guidance around offshore turbine towers has flagged condensation-related issues such as mould and corrosion as a maintenance concern, especially where transition pieces are exposed before the full turbine is installed. The operating phase is different, but the same basic pathway matters: moisture plus limited airflow plus residue creates a surface-management problem.

Biological contamination should sit inside the same disciplined HSE process as the cleaning chemistry used to remove it. HSE guidance on infections and COSHH says COSHH applies to incidental exposure to biological agents during work activities or because of the work environment, and requires assessment and adequate control of exposure to hazardous substances. The pre-trial side of that work is set out in our COSHH assessment for wind turbine cleaning.

The confined-space frame matters as well. HSE's confined spaces guide explains that some spaces are obvious, while others may become confined spaces because of the work carried out. For turbine interior cleaning, the work itself can change the risk profile by disturbing residue, introducing cleaning chemistry, changing ventilation needs or extending time in the space.

The clearest scientific evidence for microbial activity in offshore wind structures comes from foundations and monopiles, not from every nacelle or tower interior. That distinction matters. A nacelle mould finding should not be overstated as proof of structural corrosion.

Even so, offshore wind is not biologically inert. A 2025 in-situ study of microbially induced corrosion inside offshore wind monopiles found different microbial communities and corrosion behaviour at different depths. Steel specimens at 6 m were associated with iron-oxidising microbes, while specimens near 21 m were associated with sulphate-reducing and methanogenic microbes. The practical lesson for interiors is cautious: when moisture and microbes are present around coated or metallic surfaces, asset-integrity teams deserve evidence rather than reassurance.

The most useful biological-contamination inspection is specific. It should separate visible biological growth from oil, grease, dust and salt residue. It should capture where the issue appears, whether it returns, and what surfaces are affected. A vague note that says 'dirty interior' is not enough for HSE, O&M or asset-integrity review.

Photography is useful, but only if it is repeatable. Capture the same surface from the same distance where possible, note the lighting conditions, and tie images to a turbine, level, component area and date. The goal is to create evidence that can guide cleaning, not just a folder of dramatic before-and-after images.

A good wind turbine interior cleaning plan does not treat every contaminant with the same product. Oil and grease need a degreasing step. Biological contamination needs an antimicrobial approach. Dust and loose residue may need controlled removal before either treatment makes sense.

For offshore teams, the best plan is short enough to use and detailed enough to defend. It should state what is being removed, which surfaces are in scope, which product is used at which dilution, the dwell time, the removal or rinse method, and the follow-up check. That turns a messy maintenance issue into a repeatable task — and matches the way TurbineClean is intended to be specified.

Biological contamination touches more than one job title. HSE needs a defensible exposure assessment. O&M needs a task that fits the maintenance window. Procurement needs supplier documentation and product clarity. Asset integrity needs confidence that cleaning will not create a surface or coating problem.

That is why the best content, product data and trial notes should all use the same structure: define the contamination, define the risk, define the treatment, define the evidence. When those four points are clear, the conversation moves from 'is this really a problem?' to 'what is the sensible control?'