Temporary Project Ventilation: Regulations, Risks and Fan Selection

Ventilation plays a crucial role when works are taking place in an enclosed or confined space but can often be overlooked.

By ventilation, we mean forcing fresh air from into a space that would otherwise have limited or no access to it. Temporary ventilation systems often involve using fans and ducting to push and channel fresh air into a specific location where maintenance, upgrade or repair work is taking place.

Across construction, infrastructure, industry and defence sectors, work is often carried out in spaces away from the atmosphere such as:

• Tunnels
• Shafts
• Basements
• Tanks
• Ships
• Furnaces and many more

These environments are notoriously difficult to navigate, and it is vital that the workspace is assessed to differentiate the type of space, because an enclosed space will be treated different to a confined space. A confined space is a space which is substantially (though not always entirely) enclosed and where there is a reasonable chance of at least one specific risk present (e.g. toxic gas, lack of oxygen, risk of entrapment etc).  The designation of a confined space comes with expectations of formal management and additional processes, having its own regulations and standards to adhere to before work even begins. Teams carrying out works in both enclosed and confined spaces find themselves up against an ever-growing list of health and safety risks, including ensuring adequate air quality.

A temporary and reliable forced air supply system can help manage working conditions, allowing site teams to focus on the job at hand. Finding the right ventilation solution for construction works and other projects will keep the project compliant and using best practice methods will keep the team safe.

Projects typically requiring ventilation

Construction

• Basement work during top-down construction to force fresh air into excavations, diluting dust, diesel exhaust, and heat where natural airflow is insufficient

• Underground car park construction to replace stagnant air in large, enclosed volumes where natural ventilation is not viable

• Lift shafts and stair cores during construction to drive fresh air down vertical shafts to prevent stagnant air, heat build‑up, and poor oxygen levels when access points are limited

Infrastructure

• Shaft or tunnel works to push fresh air from the surface through ducting to the workforce, ensuring oxygen supply and dilution of fumes and heat over long distances

• Work in enclosed spaces such as water tanks or silos, especially when work such as overbanding is taking place and fumes can build up

• Work taking place in sewers or wastewater treatment works when toxic gases such as H₂S can build up

Read more about the risks involved in working with H₂S here >

Industry

• Hot works taking place inside furnaces during shutdown periods

• Power plant construction or refurbishment to help manages heat, welding fumes, and combustion by‑products during boiler installation, turbine works, and commissioning phases

• Shutdowns and maintenance in enclosed plants to flushes tanks, vessels, and buildings before and during entry, ensuring safe oxygen levels and dilution of residual gases

Defence

• Ship compartments during build or refit to force fresh air into enclosed compartments, maintaining oxygen levels and preventing heat buildup during prolonged work periods

• Dry dock and dockside enclosed environments to move large volumes of outside air through docked vessels where natural airflow is insufficient

• Submarine sections prior to sealing or commissioning for continuous air exchange in confined internal spaces during construction or overhaul before permanent systems are active

Health and safety risks of poor ventilation

Oxygen depletion

In a best-case scenario, inadequate air quality, or air quality that falls below safe limits can cause dizziness, fatigue, headaches and impaired judgement. In a worst-case scenario, a severe oxygen deficiency can lead to loss of consciousness or death – especially in confined spaces.

Build-up of harmful gases and vapours

Without sufficient air changes, gases such as carbon monoxide, carbon dioxide, nitrogen oxides, or residual process vapours can accumulate. The use of diesel plant, generators, curing concrete, and adjacent processes can all contribute to with even non‑toxic gases becoming hazardous by displacing oxygen.

Read our best practice guide on dealing with hazardous fumes >

Accumulation of airborne contaminants

Workers can be struck from materials falling during loading, from high platforms, accidental drops or when high-velocity works are carried out e.g. demolition, excavation, abrasive blasting etc.

Heat stress and thermal discomfort

Poor ventilation prevents heat dissipation in enclosed environments meaning workers may be exposed to elevated temperatures and humidity. Heat stress can cause dehydration, heat exhaustion, heat stroke, and reduced concentration.

Download our health and safety poster on the risks of working in summer >

Increased Fire and Explosion Risk

Poor ventilation for enclosed spaces allows flammable vapours or gases to build up rather than being diluted. Even small releases can reach flammable or explosive concentrations and ignition sources are common in construction and industrial environments.

Project risks for poor ventilation

Site team health and safety

The above health and safety risks all increase the likelihood of site teams needing sick days or longer breaks away from the working environment. Without ventilation, these may increase in frequency or duration putting additional pressure on other team members and deadlines.

Programme delays

Slower task completion due to team health, safety and wellbeing or restricted working hours in enclosed environments because conditions cannot be safely maintained. Stoppages from unsafe working environments and retrofitting ventilation late in the programme instead of installing it proactively.

Compromised integrity of works

Inadequate airflow and the impacts on personnel can reduce capabilities and endurance of teams carrying out works. Loss of concentration, slower reactions, increased errors can lead to necessary reworks, defects, snagging and more.

Escalation risks

Whether it’s a fire, explosion or serious illness on-site, events like this can become major problems leading to reputational problems, PR crisis and additional scrutiny which can put future project tenders at risk.

Commercial and financial

All the project risks listed here will impact costings on a project. Whether they’re unplanned reactive works to rectify quality of work issues or increased insurance premiums, proactive ventilation costs will be lower than rectification costs.

Non-compliance with regulations

Failure to adhere to relevant health and safety legislation can invalidate work permits and lead to enforcement action such as improvement notices, prohibition notices and even site shutdowns.

Ventilation and confined space regulations

The industry, environment and work will dictate the specific regulations and best practise that will apply to any given specific project; you should be aware of the following legislation and guidance:

• Health and Safety at Work etc. Act 1974
• Management of Health and Safety at Work Regulations 1999
• Construction (Design and Management) Regulations 2015 (CDM)
• Workplace (Health, Safety and Welfare) Regulations 1992
• Confined Spaces Regulations 1997
• Control of Substances Hazardous to Health (COSHH) Regulations 2002
• Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR)
• British Standard BS 6164:2019 (Health and Safety practices in tunnelling)

Read our detailed whitepaper on understanding COSHH regulations here >

The Health and Safety Executive (HSE) is the best source for up-to-date guidance on what is reasonably practical. If you are ever unsure, our team can perform a free site visit to assess what ventilation options may be best for your project.

RVT Group’s project ventilation solutions

Axial fans

Our VENTEX® axial fans can deliver very large air volumes of up to 34,000m³/hr, making them an excellent choice either to force clean air into a work area or to extract contaminated or stale air.

View all axial fans >

Centrifugal fans

Our VENTEX® centrifugal fans deliver airflow of up to 52,200 m³/hr and high pressure to carry it across long duct runs. Whether you require ventilation for long tunnel runs, confined spaces, or diluting hazardous environments, these fans are ideal for supplying fresh air to work areas far from the atmosphere.

View all centrifugal fans >

Axial vs centrifugal fans

ATEX rated fans

Our range of ATEX‑certified fans are built for use in potentially explosive atmospheres, helping to meet strict safety standards while maintaining effective ventilation with airflows of up to 20,000m³/hr.

View all ATEX rated fans >

Most of our fans are also compatible as part of a local exhaust ventilation (LEV) system, designed to extract and filter hazardous particulate. Read our article on LEV solutions here >

Whether you need an axial fan, centrifugal or ATEX rated fan will depend on the application and airflow requirements. Our technical consultants are on hand to help recommend a solution that works best for you.

Speak with the team today >