A few more facts about external fire doors

In our last article we refreshed our knowledge of external fire doors, covering what fire exits are and their opening mechanisms.  In this article we’re going to cover two other characteristics that along with their fire resistant properties make them highly desirable, namely their soundproofing qualities and how they help provide security.  We’ll cover each in turn.

Soundproofing qualities

Obviously and in an ideal world we don’t want the external fire door ever to have to deliver on its primary purpose – it’s a necessary precaution designed to save lives.  So for the vast majority of its time (unless it’s a dedicated fire exit of course) it’s simply a door.  We say simply, but it can provide other functions as well, such as soundproofing.

Let’s start by looking at the recommended maximum noise levels for a variety of workspaces:

Workspace	Recommended maximum noise level (dB)
Offices	40 – 45 dB
Large Offices	45 – 50 dB
Classrooms	40 dB
Large Lecture Rooms	35 dB
Music Room	30 dB

Here are some sound reduction guidelines:

20 dB	Normal speech will be readily audible
25 dB	Loud speech will be clearly audible
30 dB	Loud speech will be clearly audible under normal circumstances
35 dB	Loud speech will be audible but difficult to distinguish
40 dB	Loud speech will be faintly audible but cannot be distinguished
45 dB	Shouting will be audible but cannot be distinguished
50 dB	Shouting will be barely audible
55 dB	Shouting will not be audible

So how do we measure the noise reduction?

We’ve learned in previous articles that the Decibel is a logarithmic unit, while the percentage scale is linear. Thus, a statement like “solution XYZ would reduce noise by N dB” is meaningless.  And to emphasise the point, the Decibel scale has no maximum value, so it’s impossible to calculate a percentage reduction anyway!

We use instead a ‘Weighted Sound Reduction Index’, Rw, which expresses the difference between the sound intensity hitting one side of a structure and the resulting sound measured on the other side.

Security considerations

As we said last time, since all of the doors which are situated on escape routes leading towards the final exit should be quick and easy to open without needing a key, and there shouldn’t be any obstructions, there’s an obvious problem with the final exit door – namely, while the door needs to be easily opened from within it should not be easily opened from without.

We covered how we get around this problem by discussing the different opening mechanisms.  But how secure are they really?

External fire doors provided by Enfield Doors are tested to PAS24.  This is what the Crime Prevention website has to say about this standard:

In essence this is your guarantee that the production of the door you are purchasing is being monitored by a UKAS accredited certification body to ensure compliance with PAS 24:2012 Enhanced security performance requirements for doorsets and windows in the UK. External doorsets and windows intended to offer a level of security suitable for dwellings and other buildings exposed to comparable risk and the specific and the relevant material specific standard for general performance referenced in BS 6375 Parts 1, 2 and 3.

PAS 24, like most British Standards, is a minimum standard.  In other words it doesn’t include higher or lower grades for security and so doors that are tested to the specifications of the standard either pass or fail.  Although some of the doorsets that pass will be a little stronger than the minimum required, a minimum standard encourages engineers to design the door to pass at the minimum requirements.  This makes economic and environmental sense and the effectiveness of doors certificated to this standard has proven that the minimum levels set by the British Standards were just about spot on.

Speak to the experts

It’s been a consistent theme of our articles, not only the sheer quantity of information relating to external fire doors but the absolute necessity of getting it right.  That’s why, as we’ve said so often, it’s vital that you talk to the experts.

You can go directly to our page on fire doors if you would like more information. If you require more information you can call us on 020 3199 5864. As always we’ll be delighted to help and advise you.