Mechanical Air Ventilation

Mechanical air ventilation moves fresh air into your building and extracts stale, contaminated air under controlled conditions. Unlike natural ventilation, which relies on passive airflow through trickle vents or the stack effect, a mechanical system regulates air flow actively, so indoor air quality stays consistent whatever the weather or occupancy.

Why ventilation matters

Ventilation supplies fresh air to an indoor space and removes or dilutes indoor pollutants, controlling levels of oxygen, carbon dioxide (CO₂) and other contaminants. Without it, moisture, odours and airborne particles build up, affecting both the health of the people using the building and the fabric of the building itself.

Natural ventilation depends on passive airflow through openings, trickle vents and the stack effect, so its performance changes with wind, temperature and how the building is occupied. A mechanical system removes that variability: fans, ducts and controls set the rate of supply and extract, and filtration cleans incoming air before it reaches the space. That control is what makes mechanical ventilation the right choice for buildings with consistent occupancy, tight air quality requirements or areas that generate heat, moisture or contaminants.

Benefits of a well-maintained ventilation system

Regular inspection, cleaning and filter replacement keep a ventilation system delivering the outcomes it was designed for:

• Improved indoor air quality: Removes pollutants, allergens and odours, which matters most for respiratory health.
• Health and comfort: A constant supply of fresh air helps prevent the build-up of mould, mildew and other harmful substances.
• Temperature and moisture control: Regulates indoor temperature and manages humidity, reducing the risk of mould growth and damage to building materials.
• Reduced airborne pathogens: Dilutes and removes airborne pathogens, lowering the spread of illness in crowded or enclosed spaces.
• Energy efficiency: A well-designed system optimises airflow and reduces the need for excessive heating or cooling.
• Regulatory compliance: Keeps the indoor environment within building codes and air quality standards.

Reliable ventilation also supports productivity, since cleaner air is linked to lower sickness absence across a workforce. A planned maintenance programme is what keeps these benefits consistent rather than occasional.

Types of mechanical ventilation system

We design, install and maintain systems matched to how your building is used, including:

• Mechanical Extract Ventilation (MEV): Continuously extracts air from moisture-prone areas such as kitchens and bathrooms to keep the air fresh.
• Heat Recovery Ventilation (HRV/MVHR): Recovers heat from outgoing exhaust air and transfers it to incoming fresh air, improving energy efficiency.
• Positive Input Ventilation (PIV): Supplies a constant flow of filtered fresh air to reduce damp and condensation.
• Exhaust ventilation systems: Extract polluted air to maintain a healthy indoor environment.
• Supply ventilation systems: Deliver replacement air to prevent uncontrolled ventilation and negative pressure.

Where new equipment is specified, we use established manufacturers such as Vent-Axia and size every ventilation duct and unit to the demands of your building.

Our mechanical air ventilation services

Clean Ducts covers the full life of a ventilation system, from design through to ongoing maintenance:

• System design and installation: New ventilation, ductwork and HVAC systems tailored to the building, including energy recovery ventilation (ERV).
• Planned maintenance: Scheduled inspection, filter replacement and cleaning of air handling units, fans, dampers and controls, so the system keeps performing between visits.
• Ductwork cleaning: Removal of dust, debris and contaminants to maintain clean, efficient airflow, carried out to BESA TR19 with pre- and post-clean verification.
• Indoor air quality assessment: Evaluating air quality, identifying pollutants and recommending targeted improvements.
• Fire damper inspection and testing: Confirming fire dampers close and reset correctly, in line with BS 9999, and recording the result for your fire safety file.
• Kitchen extract cleaning: Removing grease from kitchen exhaust systems to TR19 Grease to reduce fire risk and support insurance compliance.
• Retrofitting and upgrades: Modifying existing systems to improve efficiency and meet current standards.
• Balancing and commissioning: Adjusting and verifying airflow rates for even distribution across the system.
• Repairs: Diagnosing and fixing faults in fans, dampers, controls and other components.

Standards and accreditation

Our ventilation hygiene work follows BESA TR19, the specification for the internal cleanliness of ventilation systems, and TR19 Grease for kitchen extract. Fire damper testing is carried out in line with BS 9999. Clean Ducts holds BESCA Vent Hygiene Associate membership, so your system is maintained to a recognised industry standard and documented for compliance.

Frequently asked questions

What is the difference between mechanical and natural ventilation?

Natural ventilation relies on passive airflow through openings, trickle vents and the stack effect, so its performance rises and falls with the wind, the temperature and how the building is occupied. Mechanical ventilation uses fans, ducts and controls to set the rate of supply and extract, with filtration cleaning incoming air before it reaches the space. That control keeps indoor air quality consistent whatever the weather, which is why mechanical systems suit buildings with steady occupancy, tight air quality requirements or areas that generate heat, moisture or contaminants.

How often should mechanical ventilation ductwork be cleaned?

There is no single fixed interval. BESA TR19, the industry specification for the internal cleanliness of ventilation systems, classifies systems by the air quality they need to deliver and uses measured deposit levels to establish when cleaning is due, so a healthcare ward and a warehouse sit on very different schedules. Occupancy, filtration standard and the environment the system serves all shift the frequency. We assess your system, measure what is actually inside the ductwork and set a programme through our air ventilation and ductwork cleaning service, with pre- and post-clean verification each visit.

Is maintaining a ventilation system a legal requirement?

For workplaces, in effect yes. The Workplace (Health, Safety and Welfare) Regulations 1992 require enclosed workplaces to be ventilated with a sufficient quantity of fresh or purified air, and Regulation 5 requires mechanical ventilation systems to be maintained in an efficient state, in efficient working order and in good repair. A neglected system can therefore put you in breach even if it performed well when installed. Planned maintenance, with inspection, filter replacement and cleaning documented at each visit, is the practical way to show that duty is being met.

How much does mechanical ventilation work cost?

Every system is different, so we price from a survey rather than a rate card. The main factors are the size and complexity of the system, including the length of ductwork and the number of fans, air handling units and dampers involved, how easy each section is to access, the level of contamination or wear we find, and whether the work needs to be carried out around your operating hours. Arrange a free survey and we will assess the system and return a fixed written quotation, so you know the full cost before any work begins.

Do fire dampers in ventilation systems need testing every year?

Yes. BS 9999 guidance is that fire dampers are tested by a competent person at least annually, with dampers in dust-laden atmospheres tested more frequently. A damper that cannot close removes a barrier that is meant to stop fire and smoke travelling through your ductwork between compartments, so this is not a box-ticking exercise. We drop test dampers as part of planned ventilation maintenance, confirm each one closes and resets correctly, and record the results for your fire safety file. Our fire damper testing page explains the full process.

Which type of mechanical ventilation system is right for my building?

It depends on what the building needs to control. Continuous extract (MEV) suits moisture-prone areas such as kitchens and bathrooms, heat recovery systems (HRV/MVHR) recover warmth from outgoing air where energy efficiency matters, and positive input ventilation (PIV) supplies filtered fresh air to reduce damp and condensation. Larger commercial buildings often combine supply and extract through an air handling unit. Rather than starting from a product, we start from a survey, measuring how your building performs and sizing every duct and unit to its actual demands, then design and fit the system through our ductwork and air handling unit installation service.

Request a ventilation survey

The right specification starts with an accurate picture of your existing system. Arrange a ventilation survey with Clean Ducts and we will assess your building, measure how it performs and recommend the solution that keeps your air clean, controlled and compliant.