People often ask us whether they can use fire doors as vents into smoke shafts. The answer to that question is quite nuanced but the short answer is, no. There are many reasons why, but the primary reason is due to air leakage. All smoke vents into shafts are required to undergo air leakage testing - this is to prevent smoke from spreading between fire compartments via the smoke shaft. However, this is a particularly potent issue when we come to mechanical smoke ventilation systems (MSVS).
Due to the much higher pressures involved in MSVS, air leakage becomes all the more critical. That’s why in these systems we have to use smoke control dampers, rather than any other type of vent.
I’m now going to explain which legislation and guidance requires us to use smoke control dampers:
Firstly, we have to turn page 34 of Smoke Control Association Guidance on Smoke Control to Common Escape Routes in Apartment Buildings (Flats and Maisonettes) which states that:
‘The difference in this application is that the ‘vent’ as described in ADB has to serve two functions. Firstly, it must be capable of venting heat and smoke into the shaft from the fire level; secondly, ‘vents’ on other levels away from the fire must remain closed and maintain fire separation on the other levels to prevent fire and smoke spread to the non-fire affected levels. The only product designed, tested and certified to perform both these functions is a multi-compartment smoke control damper CE marked to EN 12101-8 refer to section 8.2.'
and again on page 56:
'Smoke control dampers used should as a minimum be classified to BS EN 12101-8 as multi-compartment smoke control dampers.'
This is also confirmed by BS 9999:2017, section 6, subsection 27.1.3 which states the following:
‘Where a mechanical smoke ventilation system uses a shaft, it should meet the following recommendations. 1) The top of the lobby vent should be located as close to the ceiling of the lobby as is practicable, and should be at least as high as the top of the door connecting the lobby to the stairwell. 2) The lobby vents, in the closed position, should either: i) have a minimum fire and smoke resistance performance of 60 min and a leakage rate no greater than 200 m3/h/m2 when tested in accordance with BS EN 1366-2; or ii) be in accordance with BS EN 12101-8.’
The draft of the new BS 9991 also indicates a strong stance in relation to this:
'AOVs opening into shafts or ducts should be smoke control dampers.'
'Smoke control dampers should conform to BS EN 12101-8....'
Now you know why you need a smoke control damper, it’s also important to know what sort of damper you need.
When you’re looking at a Declaration of Performance for a damper, you should see a ‘code’ like this:
EI 120 (vew i ↔ o)S 1000 C10000 AA multi
This is formed from BS EN 12101-8 4.3.3 and 4.4.3. Here's a high-level overview of what that means:
The E stands for integrity
The I stands for thermal insulation
We can see with this example that the damper has integrity and insulation of 120.
The ‘vew’ means that the product is suitable for vertical installation in a wall. ‘Ved’ would mean that the product was suitable for vertical installation in a duct. ‘Vedw’ would mean that the product is suitable for vertical installation in both walls and ducts.
The ‘how’ means that the product is suitable for horizontal installation in a wall. ‘Hod’ would mean that the product is suitable for horizontal installation in a duct. ‘Hodw’ means the product is suitable for horizontal installation in both walls and ducts.
The addition of the symbols (i>o), (o>i) or (i<->o) indicate whether the damper has been tested and fulfills the requirements from the inside only, the outside only or from both sides.
The S means that the damper satisfactorily meets the leakage requirements. The addition of 500, 1000, or 1500 indicates the suitability of use up to these underpressures.
The C10000 means the damper has been tested for 10,000 cycles for comfort ventilation - this means that the damper can be used as part of an environmental cooling system.
‘AA’ stands for Automatic Activation. ‘MA’ stands for Manual Activation
Multi means that the product is suitable for smoke control systems dealing with multiple compartments.
That’s a whistle-stop overview of some of the key regulations around what’s known as a ‘dash eight’ damper.