Indoor air quality, once viewed as a comfort issue, is now recognised as a critical factor in public health and building performance. The COVID-19 pandemic accelerated awareness of how air circulation impacts disease transmission, but the implications extend far beyond respiratory viruses.
The World Health Organisation, the UK government, and building standards bodies are placing greater emphasis on the role of clean, well-maintained ventilation systems. Indoor air must be continuously filtered, refreshed, and moved in a way that reduces pollutants and supports occupant health.
Mechanical ventilation systems are essential for maintaining acceptable air quality in modern buildings. However, when building teams fail to clean or maintain ventilation systems properly, these systems often contribute to contamination. Dust, mould spores, bacteria, and volatile organic compounds can accumulate in ductwork and spread throughout the occupied space.
That's why many in the industry now view ventilation hygiene guided by recognised standards like TR19® as essential. Simply installing ventilation equipment no longer guarantees performance over time. Clean air delivery relies on a proactive strategy that includes regular inspection, cleaning, and accurate documentation.
For facilities managers, compliance officers, and HVAC contractors, maintaining indoor air quality is part of their duty of care. It is also increasingly tied to compliance with legislation such as the Building Safety Act and frameworks like the Golden Thread. Clean air is not just a benefit; it is a baseline expectation for safe and responsible building operation.
Ventilation systems move fresh air through buildings and remove stale or polluted air. However, without proper maintenance, these systems can themselves become a source of contamination. Understanding how and why this happens is crucial to preventing indoor air quality issues and maintaining compliance with hygiene standards, such as TR 19®.
Contamination typically builds up over time. It begins when airborne particles enter the system through intakes or internal spaces. These can include dust, pollen, fibres, and pollutants from cleaning products or building materials. If filters are inadequate or poorly maintained, these particles pass into the ductwork where they settle on internal surfaces.
Moisture is another major contributor. Humid conditions inside ducts, often caused by poor insulation or condensation, create an ideal environment for mould and bacteria to grow. In systems that serve kitchens or laboratories, airborne grease and chemical vapours can also accumulate and adhere to the duct walls.
Other familiar sources of contamination include:
Once contamination takes hold, it can be difficult to remove without professional intervention. Deposits accumulate in corners, joints, and behind access panels where airflow is restricted. Over time, these build-ups restrict airflow, strain mechanical components, and release pollutants back into the occupied space.
The presence of contaminants is not always prominent. Many systems continue to operate with reduced efficiency or subtle declines in air quality. That is why TR 19® advocates regular inspection and measurable standards for cleanliness. It ensures that systems remain fit for purpose and that hidden problems do not undermine health and safety.
Indoor air quality depends on more than just ventilation design. It also relies on how well those systems are maintained. TR 19® plays a key role in helping building operators meet their indoor air quality (IAQ) goals by setting consistent, evidence-based standards for the cleanliness of ductwork and ventilation components.
TR19® provides a structured approach for assessing and maintaining hygiene levels in both supply and extract systems. It includes detailed guidance on how to inspect ducts, measure contamination and carry out cleaning where necessary. Such an approach helps ensure that systems deliver clean, healthy air throughout the building's lifecycle.
One of the standard's core strengths is that it offers measurable benchmarks. Using tools such as the Deposit Thickness Test (DTT), engineers can determine whether the internal surfaces of ductwork are within acceptable cleanliness limits. These results can be documented and tracked over time, ensuring that building owners, insurers, and regulators are assured.
TR 19® also promotes system accessibility. The standard outlines how teams should design and install ductwork to facilitate regular inspection and cleaning. This approach strengthens ongoing hygiene management, allowing facilities teams to uphold IAQ standards without disruption.
In buildings governed by the Building Safety Act or those requiring enhanced compliance, TR 19® supports the Golden Thread of building information. Its focus on documentation and traceability helps teams demonstrate that they have maintained ventilation systems to a recognised standard.
By following TR 19®, facilities managers, consultants, and contractors are not only keeping systems clean. Additionally, they are actively contributing to improved air quality, enhanced occupant wellbeing, and long-term regulatory compliance. The standard is not just a technical document. It is a practical tool for delivering healthier buildings.
Good indoor air quality, supported by regular ventilation hygiene in line with TR 19®, delivers clear advantages to everyone involved in a building's operation and use. From improved occupant health to lower maintenance costs, the benefits extend across the supply chain.
Businesses that prioritise ventilation hygiene create a healthier working environment for their staff. Clean air contributes to reduced absenteeism, improved concentration, and better overall productivity. Maintaining clean air is especially important in sectors where staff spend long hours indoors, such as offices, education, retail, and healthcare. Maintaining ventilation systems in accordance with TR 19® also demonstrates a company's commitment to employee welfare and regulatory responsibility.
Tenants want assurance that the air they breathe is clean, safe, and free from contaminants. When ventilation systems are adequately maintained, indoor spaces tend to feel fresher and more comfortable. Clean, well-maintained ventilation directly improves tenant satisfaction and reduces complaints about stale air or poor environmental conditions. TR19 supports this by requiring regular inspections and documentation, helping building managers demonstrate that systems are well-maintained.
For those managing multiple systems or large estates, TR 19® offers a clear framework that simplifies compliance and maintenance planning. It enables more accurate budgeting, supports insurance requirements, and helps avoid emergency callouts or costly system failures due to poor hygiene. Facilities managers can utilise TR 19® inspection reports and deposit test results as part of their Planned Preventive Maintenance (PPM) schedules, ensuring that performance standards are maintained year-round.
TR 19® also reduces uncertainty between stakeholders. With one agreed-upon standard in place, building owners, contractors, and clients have a shared understanding of what constitutes good ventilation cleanliness. Clear documentation enhances communication, mitigates project risks, and fosters the long-term sustainability of the building.
Maintaining indoor air quality is not a one-time effort. It requires a structured, ongoing process of monitoring, inspection, and maintenance. TR 19® provides the framework needed to ensure that ductwork remains clean and that ventilation systems continue to perform safely and efficiently.
Routine monitoring involves tracking system performance indicators, including airflow rates, pressure drops, and filter condition. These values help identify when an obstruction or hygiene issue may be developing inside the system. In high-risk environments, such as kitchens or healthcare facilities, continuous or periodic monitoring is crucial for early intervention.
TR 19® outlines how and when teams must inspect ventilation systems. It recommends visual assessments, measurement of deposit thickness, and photographic documentation. The frequency of inspections depends on the building type, use, and risk level. For example, kitchen extract systems often require quarterly checks, while general air supply systems may follow annual or biennial schedules.
All inspections should be recorded and stored as part of the building's operational documentation. These records help demonstrate compliance with the Building Safety Act and support the Golden Thread of safety information now expected for many buildings.
Teams must schedule cleaning based on inspection findings and the levels of contamination present. TR19® provides specific thresholds that trigger when cleaning is necessary. The use of approved cleaning methods and access equipment is essential to ensure thorough and safe maintenance.
Incorporating these protocols into a Planned Preventive Maintenance (PPM) schedule ensures that ventilation hygiene does not fall behind. It also allows facilities teams to allocate resources more effectively and reduce the risk of emergency repairs.
By embedding these processes into everyday building management, organisations can meet both their legal obligations and their performance goals. TR19® helps simplify that task by providing a clear, consistent standard to follow.
For a complete overview of how ventilation hygiene supports safety, compliance, and long-term system performance, read our TR 19® Ventilation Hygiene Standards Guide.
If your role involves kitchen systems or grease extract maintenance, explore:
Maintain cleaner, safer indoor environments with expert guidance from BESA.
Download the TR 19® Guide