Hygienic - Extract Ventilation

Kitchen Extract Ventilation Ductwork

What Is Kitchen Extract Ventilation Duct Cleaning?

It is a well-known fact, that ventilation systems are installed in buildings in order to ventilate the rooms. The system is designed to supply or extract a certain amount of air to the rooms. Even with filters fitted to the extract system, the internal ductwork will become heavily deposited with grease, carbon, dust etc refer to the above images. Contaminants accumulate and must be eradicated by cleaning using various cleaning methods as described in the ‘cleaning phases’ listed below, to eliminate Fire Hazard and to maintain the ventilation system in working order.

Why Is It Necessary?

The efficiency of an extract system is reduced when it is contaminated with grease. Kitchen and extract ducts have since long been recognised as a major fire hazard. There have been countless fires over the years. The most significant reason for this is inadequate cleaning of the interior of extract ducts. Every building with cooking facilities has a potential risk of fire that can not be overlooked. Contamination of areas remote from the hood are considered difficult to reach and therefore often not maintained. A dirty ventilation duct creates a fire danger. Grease and dust burn very easily and with suction in the duct system, the fire can spread out to other parts of the building rapidly. A new law came into effect in April 1st 2006 Fire Safety Order 2005 The Regulatory Reform (Fire and Safety Order 2005) Insurance losses resulting from fires in kitchen extracts have risen rapidly, experts now recommend cleaning kitchen extracts as per table 11.

Recognized Trade Association

We are a member of the B&ES (formerly HVCA - Heating and Ventilation Contractors Association) The HVCA Ventilation Hygiene Group Branch has investigated a variety of methods for testing ductwork system internal surfaces to measure grease deposits and recommends the Wet Film Thickness Test (W.F.T.T) measurement method. The Deposit Thickness Test (D.T.T) may also be used and maybe necessary in the case of extremely hard-baked, carbonised, deposits. Testing to be carried out at intervals not exceeding 12 months and as recommended in table 11. Monitoring of grease deposits may need to be carried out more frequently if it is necessary to establish a precise definition of required cleaning frequencies. Cleaning is carried out as per HVCA Guide to Good Practice TR/19.

Ventilation Cleaning Strategy

Primary contact

This gives us as a company the chance to discuss with the client the location and his requirements

Site inspection

Engineer to attend site to compile inspection to the clients and system requirements. Access inspections hatches are required in order to view the internal ductwork to ascertain cleaning methods/ requirements etc most suitable for the site.


After the site inspection, it is usually possible to offer a quotation and cleaning programme.

Cleaning methods:

There are two types of cleaning, the wet and the dry method, both using several different techniques. All methods used are up to-date to create minimal fuss to our clients and environmentally friendly.


The actual cleaning is carried out upon the basis of the inspection and as recommended by HVCA refer to table 11, in a way that is best for the given system taking into account the cooking operations.


A report shall be provided to include

  • Pre-clean measurements
  • Post-clean measurements
  • Photographic records
  • Additional works carried out (if any)
  • COSHH data on any chemicals used
  • Recommendations for future cleaning requirements
  • Observations on the condition of the ductwork system

After service:

Upon completion of the initial clean , a service agreement with the customer can be arranged to suit their cleaning requirements, to ensure their ductwork system is correctly maintained to make sure the system is functioning efficiently and to prevent a fire hazard.

Table 11: Frequency of Cleaning
Heavy Use 12- 16 hours per day 3 monthly
Moderate Use 6 - 12 hours per day 6 monthly
Light Use 12 monthly


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