OVs vs AOVs. What do you need in your project?

By Sam Gocher
Tuesday 5th September, 20232 minute to read

Welcome back to another blog from Sertus. In this edition we’re going to be discussing what Opening Vents (OVs) are, and where they can be used, in comparison to Automatic Opening Vents (AOVs).

An OV is still an electrically operated vent, it’s just not automatic. It’s usually operated by a firefighter’s priority switch or a key switch. However, you need to remember than an OV is still a piece of firefighting equipment and should only be used by firefighters, not by residents.

OVs are only used in small single stair buildings. There’s a strict set of criteria in Approved Document B that must be met if they’re to be used. The criteria found in Approved Document B Section 3 – all of these criteria must be satisfied if an OV is to be used. These are as follows…

  • The top storey of the building is no more than 11 metres above ground level.

  • There are no more than three storeys above the ground storey.

  • The stair does not connect to a covered car park, unless the car park is open sided.

  • The stair does not serve offices, stores or other ancillary accommodation.

On that last point, if it DOES then there are further considerations in Approved Document B. There are also further considerations for bin stores and rubbish shoots. Finally, either of the following must be provided for the fire & rescue services.


A high level openable vent with a free area of at least one metre squared at each storey.


A single openable vent with a free area of at least one metre squared at the head of stair, operable remotely at the FRS access level.

If all of the criteria are met, then OVs can be used, if one or more aren’t met then AOVs will need to be used. It’s worth remembering that AOVs must be used in all buildings other than small single stair buildings. Sertus have a wide array of AOVs on our website – click here to view our product page.

If there’s anything we can do to help your smoke ventilation and access hatch endeavours, please do contact us. Thanks for reading.

Related Articles.
What's the best AOV on the market? You decide...
Read More
RLB-R: Everything you need to know about our louvred AOV!
Read More
Can you use an AOV as an access hatch?
Read More
Get in touch.
Want to learn more about our products? 😊
Talk to us