Advantages of hatch and louvred stairwell smoke vents (AOVs)

A stairwell smoke ventilator is an automatic opening ventilator (AOV) which provides at least 1.0m2 of free area when open. It usually serves one of two purposes;

  1. To evacuate any smoke that gets in the stairwell of small buildings
  2. Or more commonly it provides replacement air for a lobby smoke extract system in large buildings

There are two main types of smoke ventilators, used at the head of a stairwell – louvred vents and hatch vents. Both types of vents are able to perform the expectations of an AOV, however each have individual benefits which will influence the selection process.


Download Easivent's pocket guide to stairwell AOVs


Louvred vent benefits

  • Louvred ventilators can be used for daily ventilation, either by adding a rain sensor to the control system, or by selecting a louvre with separate side mounted daily ventilation louvres to allow fresh air input without opening the whole louvre. This means that daily ventilation can be provided even in wet weather. 
  • Louvred vents have a low profile when installed, which means the vent is less likely to incur wind damage when open. This is a frequent cause of damage to hatch ventilators which are opened in high winds.
  • Even when open, intruders will not be able to gain access to the building through the vent.

Advantages of louvred stairwell AOV

Closed louvred vent

Hatch vent benefits

  • The lid opens to over 120o to ensure smoke exhaust benefits from cross winds and has no obstructions.
  • The free area of a hatch vent is maximised as there are no obstructions to airflow therefore the roof opening size is slightly smaller than the equivalent louvre.
  • An insulated hatch vent will have a better u value than the equivalent louvre giving a better insulation performance.
  • Hatch vents may also be used for roof access.
    • Using hatch vents for roof access will require the opening mechanism to be designed in such a way that it doesn’t obstruct access through the hatch. In addition, manual controls to facilitate the opening and closing both from inside and from the roof can be installed.

Advantages of hatch vents AOV

Open hatch vent

A range of hatch and louvred vents are available on the Easivent webstore, or download our guide for more information. 


Download your AOV kits guide


Under the Construction Products Regulations (CPR) it is a legal requirement to use only certified products for smoke ventilation. For more information see SCS Group’s Technical Bulletin here.

Find out more about automatic opening vents on our information page here.

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