Imtech NHS CNWL – Ventilation Hygiene Assessments


Imtech Inviron Ltd are a facilities management firm based in Birmingham, UK who have numerous national contracts across the country, one of them being with the Central and North West London NHS Foundation Trust. As part of their contract and Planned Preventative Maintenance agreements there was a requirement to carry out Ventilation Hygiene Assessments across multiple sites in the portfolio.


Due to these sites being healthcare premises, they have to follow a slightly different set of specifications (HTM-03-1) to ensure they are of a higher standard than other buildings. This also placed an increased emphasis on the quality and quantity of air being exchanged and delivered throughout this project to ensure the vulnerable people within these sites didn’t pick up any other infections.

With many of the sites being healthcare premises for mental health patients, there was the additional challenge of our engineers accessing all the ventilation extract and supply grilles within these buildings.


Regarding the problem of access to certain areas within the building, we were able to use our extensive experience of work on similar sites to work with the client to create a solution which would allow us access whilst causing a minimum amount of disruption to everyone within the building.

With the assistance of our PST team, we were able to get into all of the Air Handling Units and Ventilation Ductwork systems at each site and take Deposit Thickness Tests (DTT) all within seven days. These DTTs are taken to measure the levels of contamination present within a ductwork ventilation system. These samples were then incubated to investigate the extent of microbiological growth within each system which resulted in multiple sites requiring immediate TR19 standard cleaning according to the levels deemed acceptable under HTM-01

Value added

On completion of the project and a formal review of the Post-Inspection Reports, including images of each AHU where samples were taken. Furthermore, recommendations were made to ensure the systems were adequate for use and delivered on their promises. Common recommendations include replacing Bag Filters & Fan belts, as well as carrying out cleaning to TR19 standards. Some of these replacements are currently being investigated and surveyed to implement this year.


To find out what our Air Hygiene Ventilation assessments include, visit our dedicated page

Corrosion within ductwork
Ductwork corrosion
Scale present within water system
Scale present within unit
Worn bag filters
Worn bag filters