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If you can't stand the heat...

Kitchen ventilation is simple in principle, but there is still a lot of rubbish spoken about it. Steve Leonard expels some of the hot air
The essentials of kitchen ventilation are simple. Air has to be removed and replaced constantly, and enough air has to be removed to take away deadly combustion fumes and unpleasant cooking odours. Yet surveys and the day-to-day experience of the Health & Safety Executive (HSE) suggest that up to 65 per cent of commercial kitchens are not ventilated adequately.

Catering can be highly rewarding, but while 'slaving over a hot stove' may be acceptable to some, there are many health and safety concerns about working in a hot, steamy and grease laden environment.

Far too many free-standing fans are used for cooling. These can be a huge safety hazard in a kitchen, putting people at risk from electric shock and tripping over trailing cables. They also risk spreading unhealthy micro-organisms and may create disruptive air movement that harms the efficiency of a ventilation system that's already in use.

HSE information sheet 'Ventilation of Kitchens in Catering Establishments' (catering sheet number 10) offers advice on good ventilation practice. It suggests that removal of 'used' air and fumes must be balanced by the draught-free provision fresh air that has to come from 'clean' areas.

The HSE especially recommends hoods for coping with extraction above gas-fired and any other appliances capable of generating heat, water vapour, fumes and odours.

The Executive estimates that around 85 per cent of the total air needed in a kitchen tends to be supplied by mechanical ventilation, with the rest coming from adjoining areas. This keeps the kitchen under negative pressure, helping to prevent the escape of cooking odours.

Kitchen ventilation rate
The accepted recommendation is a kitchen ventilation rate of at least 17.5 litre/sq m of floor area, or 30 air changes an hour. This is fine in summer, but may not be so in winter when more controllable ventilation is frequently required.

Systems must also comply with British Standard BS6173:2009. This requires interlinking of mechanical ventilation systems and gas supplies for all types of commercial kitchen appliances, preventing a unit from being switched on before the ventilation system is operating.

Besides evacuating fumes, systems need to avoid a build-up of grease in ducting and prevent insect pests being drawn in with replacement air.

The HSE points out that it is possible to naturally ventilate using replacement air brought in through wall grilles, doors and windows. But, any air fed into the kitchen should come from clean areas where pest entry can be controlled and tobacco smoke is absent.

Poor ventilation presents three types of risk - personal health, food hygiene and third parties.

A good balance of incoming and extracted air together with removal of hot vapours at source should help prevent kitchens becoming too hot. The replacement air inlets can be positioned to provide cooling air over any hotter work positions. And if this isn't enough, an overhead air outlet can be incorporated to discharge cool air.

Induction hoods offer the best control over kitchen heating and ventilation but, whichever system is chosen, it pays to work with experienced suppliers who are familiar with the latest standards, regulations and guidance.

Complementing the HSE advice are two publications from the Building & Engineering Services Association (previously the HVCA). DW/172 is the 'Standard for Kitchen Ventilation Systems', while TR/17 is the 'Guide to Good Practice, Cleanliness of Ventilation Systems'.

// The author is managing director of Ledaire Fabrications //

1 March 2012

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