Analox Sensor Technology

If you can’t stand the CO2, get out of the kitchen – Part 2

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Courtesy of Analox Sensor Technology

In Part 1 we reviewed the many standards, specifications and technical bulletins on commercial kitchen ventilation that have been published since 2000. In Part 2 we investigate four of the more recent ones, with a particular focus on carbon dioxide (CO2) monitoring in commercial kitchens. These publications are:

A commercial kitchen is generally defined in British Standard BS 6173 as a catering area that prepares meals for the public—in contrast to a primarily domestic setting such as a Bed & Breakfast. The Institution of Gas Engineers & Managers, in their document IGEM/UP19/Edition 1, use a broader definition, which includes, ‘…catering establishments that fall within The Food Safety (General Food Hygiene) Regulations.’

BS 6173 specifies that ventilation must be provided in public catering areas to ensure both the introduction of fresh combustion air for cooking and the removal of steam and other products of combustion. Standard IGEM/UP/19 states that, ‘natural ventilation could achieve adequate air quality [… ] but, for small spaces with a large cooker or large catering installations,[…] mechanical ventilation would normally be required’.

CO2 gas is a reliable indicator of the effectiveness of kitchen ventilation. IGEM/UP/19 states that for newly designed kitchens, the CO2 level in staff working areas should be less than 2,800 parts per million (ppm) and that the kitchen appliances—or their gas supplies—should shut down if CO2 is above this level. For existing installations, appliances or gas supplies should shut down if the concessionary 5,000 ppm limit is reached.

Raised CO2 levels may be caused by a problem such as blocked filters in a cooker hood or insufficient fresh make-up air. Whatever the cause, it could lead to a dangerous situation. An increase to 15,000ppm (1.5%) CO2 may cause drowsiness, headache and increased breathing. 30,000ppm (3%) CO2 could cause dizziness. If the concentration exceeds 100,000ppm CO2 (10%) this may lead to unconsciousness or even death. BS 6173 requires kitchen appliances to be interlocked with any associated mechanical ventilation systems, to enable automatic shutdown of the appliance. For example, a cooker extract canopy must be interlocked with the cooker (or its gas supply) to ensure that if the canopy fails—or is accidentally switched off—the cooker is automatically shut off. This prevents any further combustion until the canopy failure is resolved.

IGEM/UP11/Edition 2 recommends that in cases where a kitchen’s ventilation requirements are unlikely to be met, fixed CO2 monitoring may be installed in the general kitchen environment—i.e. not under a hood or canopy—to form part of the interlock system. This is further discussed in IGEM/UP/19.15 (section 5.1.2), which also points out the difficult environmental conditions facing CO2 detectors in a commercial kitchen. Kitchen ventilation manufacturers sometimes integrate CO2 sensors into their products in order to provide demand-based ventilation. These built-in sensors are used to constantly monitor the CO2 level and adjust the ventilation to maintain an appropriate air flow. This provides ventilation that is appropriate to the level of cooking activity, minimises the energy used and ensures the system operates only when it needs to.

‘Air quality testing’ is another essential process for any commercial kitchen ventilation system. Air quality is tested during both the commissioning phase and the subsequent periodic maintenance activities. BS 6173 explains the importance of testing air quality, recording the results and taking remedial action. IGEM/IG/2 Communication 1772 (2015) discusses the use of hand-held monitoring devices to measure carbon dioxide.

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