How much ventilation is needed to make car parks safe?

Posted by Conor Logan on 18/10/12 12:01

Carbon dioxide coming out of a car exhaustAs National Carbon Monoxide Awareness Week approaches (19-25 November), we ask what is the best approach to designing a car park ventilation system that guarantees good air quality at all times.
The requirements

Regulations in Approved Document F (ADF) stipulate that sufficient ventilation must be provided to enclosed car parks to avoid an excessive build up of carbon monoxide (CO), which should average less than 30 parts per million (ppm). The ventilation system must be designed to maintain CO levels within approved levels during peak hours and under the worst possible conditions – for example, where there is a line of queuing cars inside the car park. The ADF goes on to suggest providing for six air changes per hour (ACH).

A one-size-fits-all approach can be expensive

That is a useful guide, but CO levels in a car park will vary during the day, depending on the levels of traffic. Also, car parks can present very different patterns of use: in a shopping centre, they will be very busy during trading hours, but in an office building, there will be two strong peaks of activity in the morning and at the end of the business day.

The full six ACH is generally only required to deal with peak conditions, so running the car park ventilation system at this rate all the time is likely to result in unnecessarily high energy consumption and, consequently, high operating costs.

A flexible approach is best!

Fitting CO detectors throughout the car park and linking them to the ventilation system’s controls ensures that the ventilation rate is constantly adjusted according to the CO levels. This way, the ventilation system will run at the full six ACH at peak times, but at lower rates when the car park is not as busy.

This will add to the initial costs, but result in significant savings in energy expenses throughout the life cycle of the system – and keep the car park’s users safe from the harmful effects of carbon monoxide.


Conor LoganConor Logan is a Technical Manager of Colt UK, Smoke and Climate Control Division. Conor is also Chairman of the Smoke Control Association.

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Topics: Regulations, Smoke ventilation, Car Park Ventilation