Extract danger

This startling figure was produced by a survey carried out by HVCA member Indepth Hygiene Services. Martin Turner, operations manager at Indepth Hygiene’s extract ventilation division, inspected over 350 kitchen extract systems during an 18 month period. He found that the vast majority were so dirty they represented a serious fire hazard. “More than 90% of the systems weren’t bad, they were appalling,” he comments. “People only see the cooker hood and filters and never think about the grease extract ductwork behind them, which often runs through the whole building.”

An extract ventilation system is designed to draw grease-laden air out of a kitchen via the extract canopy, through a system of ducting to an external exhaust. Filters in the cooker hood trap some of the grease, but even those that are clean and in good condition cannot remove all of the grease and oil suspended in the extracted air. Some of the remaining particles bypass the filters and are drawn through the system. As the air cools, a certain percentage is deposited on the inside of the ductwork and the extract fan itself. Over time, these grease builds up, and the only solution is to gain access to the ductwork and physically remove it.

Meeting the standards
The recently revised Heating and Ventilating Contractors’ Association (HVCA) standard TR17: Cleanliness of ventilation systems, specifies a maximum recommended acceptable level of contamination on the inside of extract ductwork.

It also recommends that grease extract ductwork is cleaned at intervals of between three months and one year, depending on the level of usage of the cooking equipment.

“Every grease extract system should be inspected regularly by a competent contractor,” states Turner. “These inspections will then indicate the frequency of cleaning required to meet the cleanliness levels laid down in TR17, which should be annually as a minimum.”

Dirty grease extract ductwork is not just a threat to food safety and hygiene. A far greater risk is fire, as even a small flash fire on the hob can easily ignite grease lining the ductwork behind the cooker hood. Flames and heat can quickly spread along the ductwork to other parts of the building, causing major damage or destruction of the property and putting lives at risk.

“There are 50 large fires every year involving commercial cooking and extract ducts in London alone,” advises Jim Golt, divisional officer for fire safety at the London Fire Brigade. “Fortunately there have been no fatalities, but over a five year period these fires have caused 19 injuries and eight people had to be rescued as a result.”

Losses resulting from fires in neglected kitchen extract systems have risen sharply in recent years, a fact that has not gone unnoticed by insurance companies. “Insurance companies and fire brigades are increasingly recognising the fire hazard represented by poorly maintained grease extract systems,” says Turner. “Some insurance companies now require a risk assessment of the kitchen to be carried out before fire cover is provided, and insurance policies may now specifically exclude liability for fire damage where the extract system has not been cleaned on a regular basis.”

A guidance document on fire risk assessments for catering extract ventilation systems has been prepared by the Building Services Research and Information Association (BSRIA) in association with the Association of British Insurers (ABI). Steve Birt, ABI’s assistant manager of commercial property says: “The principal fire risk in extract ventilation is created by the excessive build-up of cooking oil deposits.”

The guidance document recommends that extract ductwork should be inspected at least annually by a competent contractor. It also repeats the guidance given in TR17 for cleaning intervals depending on use of the equipment.

“By following this assessment you will prevent the build-up of grease deposits within the kitchen extract ventilation, which will reduce the risk of spreading fire, the growth of bacteria and odour, and improve airflow through the kitchen,” says Birt. “Also bear in mind that if you do not take suitable precautions, and in the event of personal injury or death resulting from a fire associated with a poorly maintained system, charges of corporate liability or manslaughter may be brought against the kitchen operator,” he concludes.

One problem that Indepth Hygiene often encounters is determining who is responsible for the extract system. The catering manager often believes that their responsibilities end at the cooker hood, while the facilities manager assumes that the kitchen extract is looked after by the catering department.

“Often when we go in to survey an extract system no one knows where in the building it runs,” says Turner. “The situation is made more complicated where the catering is contracted out, and often no one has thought about the kitchen extract for years.”

When the ducting is located it is often in inaccessible parts of the building. Even if inspection hatches have been supplied at the time of installation they usually lack adequate provision for cleaning. To properly clean extract ductwork, access panels of at least 300 x 100 mm are required every three metres. If these were not included in the original ductwork installation they need to be cut before cleaning can begin. Grease also builds up on the fan itself and any dampers in the system, and these too need to be thoroughly cleaned.