How do I choose the right size chain length?

The length of the chain is specified by the free area required for smoke to escape. Approved Document B states that vents within lobbies should have a free area of 1.5m2, while stairwell vents should be a minimum of 1.0m2 and should open fully within 60 seconds. Under the Construction Products Regulations (CPR), it is a legal requirement to use only certified products for smoke ventilation. It is the responsibility of the installer to ensure installations meet the relevant standards and products are fit for purpose.

You can use our online calculation tool located the resource section of our website.