The dangers of the hot motor test in BS 8524-1:2013

It’s 400°C and your fire curtain motor is still working… 


Or dangerous?

BS 8524 is such a comprehensive standard and has all these extra tests…

One is the hot motor test.

BS 8524-1 requires fire curtains to conduct a hot motor test, where the motor must operate 12 times over 30 minutes with the furnace temperature at 400°C ± 20°C.


Or dangerous?

Are the extra tests in BS 8524 a good thing? We aren’t the first to raise this. Conor Logan, Technical Manager of Colt UK, wrote of his concerns back in January 20161

Hot water burns us at around 70°C.

It scalds us at 100°C.

The emergency services would not open a fire curtain with the temperature at even half of 400°C as it would exceed the limits to which firefighters are trained; see “Characterizing a Firefighter’s Immediate Thermal Environment in Live-Fire Training Scenarios” which states “severe training conditions generally [exposed firefighters to] temperatures between 150°C and 200°C”2

A fire curtain should never be operable if there are temperatures of 400°C on one side, as this would pose a severe-to-fatal risk to the operator and could allow the fire to pass beyond the designated compartmentation barrier and thus endanger the whole building.

It could be argued that the hot motor test is for applications where the motor is high above the operator, for example in a ceiling void. In this situation, if there were a fire in the void and not lower down, and if you wanted to operate the fire curtain, you have a rare combination where a hot motor use may be applicable.

But what is the incidence rate of this combination, and who is going to stop the curtain from opening above the safe temperature limit so as to prevent the fire from spreading? If it is 400°C up where the motor is, and 20°C down where the operator is, it stands to reason there is a temperature gradient in-between.

What is the safe amount to open the curtain to? Who is going to know this, let alone do it when escaping from a fire?

To justify this test being of potential value, data is required to show how often this combination occurs, and a control measure is required including easy-to-use instructions by the user in a fire situation, so they don’t open the fire curtain too far and thus endanger the building further. A failsafe back up to stop the fire from spreading is also required in the event of user error. Otherwise, this is a dangerous capability, and the motors should be designed so they do not work at elevated temperatures, the exact opposite of what the British Standard calls for.

The capability for an untrained person to operate the motor at 400° in the vast majority of circumstances is dangerous. Whilst this test may have the best of intentions, on the balance of risk that it poses in its current format versus any benefit it may provide in very rare circumstances, it should be removed.

Note. Even if this test were a good thing and if it could have benefits somewhere, the expansion of the bottom bar at 400°C is untested and it is very questionable whether the motor would be capable of moving the curtain if the bottom bar had expanded and jammed in the guides.

The above is an extract from the Adexon white paper, A technical comparison of BS EN 16034 and BS 85243.

Commercial interest should have no influence on safety standards.


1 Logan, C. (no date) Have testing regimes in standards got out of touch with reality?, Colt Blog. Available at: .

2 Willi, J.M., Horn, G.P. and Madrzykowski, D. (2016) Characterizing a firefighter’s immediate thermal environment in live-fire training scenarios – fire technology, SpringerLink. Available at: .

3 Adexon Team (2023) A technical comparison of BS EN 16034 and BS 8524.