Classroom Function and Anti Barricade Function are two upgrades available on the cylinders that we supply. Both are specialist options for different scenarios but it can be easy to get them confused. Here we set out the differences and when you might need to use them;

Classroom Function

This function, as you would imagine from the name, is used mainly in schools on classroom doors.

Generally classroom doors are required to be lockable, however an internal thumbturn is used for rapid egress in the event of a fire. The difficulty with this is that students can potentially lock the door from the inside and even hold the thumbturn in the locked position, preventing it from being unlocked from the outside.

The Classroom Function is a way of preventing this from happening. Put simply, it allows the internal thumbturn to rotate only in one direction. Hence a door can only be unlocked from the inside, not locked. The mechanism is handed left or right depending on which way the lock operates – it’s important to check the handing is correct otherwise it will have the opposite effect and only allow the thumbturn to lock the door but not unlock it!

Simply specify if you want the thumbturn to rotate clockwise or anti-clockwise when ordering.

If the handing ends up being incorrect for any reason, the mechanism can always be reversed on site and we supply the kit to do this.

Anti Barricade Function

Again, the name says it all. The Anti Barricade Function uses a clutch mechanism within the cylinder to allow the key to operate and unlock the door even when the thumbturn is being held in the locked position on the inside. Hence it helps to prevent someone from barricading themselves into a room.

This function is often specified in psychiatric units or hospitals and enables staff to gain access in an emergency without damage to the lock or door.

Anti Barricade Cylinders are not handed, so they are more straightforward to supply and install than the Classroom Function Cylinders. However they don’t prevent the door being locked from inside the room. This has traditionally meant that this function has not been used in schools. However, with the increasing need for lock-down procedures in schools it’s become important to be able to lock classroom doors from the inside, meaning that the Anti Barricade function is becoming far more widely specified for these environments.

We find that, whilst a lot of attention is given to the installation of intumescent hinge pads, fitters can sometimes be less aware of the intumescent requirements of mortice locks. However, when you consider the amount of timber that needs removing from a door to install a mortice lock, you realise how critical this is to fire integrity.

As always, we have to go by the fire test evidence, and it’s essential that the lock you are installing has been tested for use in a fire door.

Fire door test evidence

The most important thing is to check this and be guided by it.

Generally speaking, most fire door assessments will require an intumescent wrap that goes around the lock body, under the forend and also under the keep. For FD30 purposes, this will usually be required to be 1mm thick. For FD60 purposes, some or all of the wrap may have to be 2mm thick.

There are some exceptions, for instance the Flamebreak 30 door blank Certifire Certificate states that no intumescent is required assuming the lock falls within certain size and specification parameters.

Other things to check on the fire test assessment are;

1. Maximum lock, forend and keep dimensions. Generally door cores will have been tested with all regular sized locks including DIN standard locks, but you should check this, especially if you have a large/unusually shaped lock body
2. Lock positioning. There will usually be a maximum and/or minimum height that the lock can be installed at, make sure you are aware of this!
3. Any forbidden door/design configurations, eg. rebated stiles.

Mortice lock test evidence

Where the fire door test evidence is not available, you should always go by the lock’s fire test evidence.

For example, we normally specify DIN Standard locks from our LZH600 range. These locks are Certifire, CE and UKCA Marked, and suitable for FD30 and FD60 fire doors.

Some details from the test evidence for these locks is listed below;

For FD30 timber doors, the Certifire fire test evidence requires that 1mm thick Mono Ammonium Phosphate or graphite-based intumescent sheet material is fitted aound the lock case and behind the forend and strike plate.

For FD60 timber doors, the same is required but the intumescent behind the forend and strike plate should be 2mm thick.

There is also an additional note for FD60 applications to say that the door/frame perimeter intumescent should bypass the strike plate or forend by a minimum of 7.5mm wide on each side (with the exception of the latchbolt lead where present).

In conclusion we can say that if you are fitting a lock into a fire door, it’s highly likely that you will need to fit an intumescent wrap with it. Consequently when quoting/specifying we will always allow for a 1mm thick intumescent wrap to FD30 doors and a 2mm thick intumescent wrap to FD60 doors.

Our wraps are made to fit the locks precisely and just need folding around the lock. There are also holes to match the spindle and lock positions, so fitting is really simple.

Intumescent door edge seal is a critical component in a fire door.

In the heat of a fire, the intumescent material will expand to fill the gap between the door and the frame, thus ensuring the fire integrity of the whole doorset. The longer the door is required to resist the fire, the more intumescent material is needed. Hence there are several different sizes of seal available.

As standard, the seals are all 4mm deep, but the widths vary to accommodate different amounts of intumescent material. The most commonly used widths are 10mm, 15mm and 20mm. In general, the 10mm and 15mm widths are used for FD30 doors, whilst the 20mm width is used for FD60 doors.

The seals should be fitted centrally in the edge of the door, or in the frame opposite the centre of the door edge. If you are using 2 strips along the edge of the door, these should be centred on the centre of the door edge.

However it is very important that, if possible, you consult the test evidence of the door itself and be guided by this.

For instance, very often in door fire assessments a 15mm wide strip is required even for FD30 doors. For this reason we would recommend using 15mm seals on an FD30 door if in doubt.

Extra intumescent is also generally required for double doors, and when a door leaf is extra large. In fact, any doorset other than a standard single action single door should be treated with caution.

In these cases it’s extra critical to consult the door test evidence. This will usually give guidance for pretty much every scenario. For instance, the Warrington Fire Field of Application report for the Strebord 44 and 54 doors has over 150 pages of guidance about what seals should be used in every different scenario!

Below are some potential pitfalls to watch out for;

1. Installing seals that are smaller than required – there simply isn’t enough intumescent material to hold the fire at bay for long enough
2. Fitting seals in the incorrect position – seals should be centred around the middle of the door edge. If they aren’t, you risk the intumescent material forcing the door open when it expands.
3. Using seals that are much larger than required can even have the same effect of forcing the door leaf open and compromising the fire integrity
4. Using larger seals is not a solution to compensate for large gaps around the door! If door edge gaps are too large, the door is unsafe and needs adjusting or replacing.

The most common design of fire door sign is a 76mm diameter disc with a blue background and white contrasting text. There are several versions to be used in different situations:

Fire Door Keep Shut

This is the most commonly used fire door sign. It should be fitted on fire doors that are self closing and used for the passage of people. One should be mounted on each side of each door leaf. A fire door should never be held open in any way because if it’s open it can’t perform its function of preventing the spread of fire. 

Fire Door Keep Locked

This sign is fitted on doors that aren’t frequently being operated and aren’t used for passage of people. Typical door types are riser doors and small store cupboards. The door must have a lock (obviously!) but doesn’t need a door closer as you are relying on the lock to keep the door held shut in a fire scenario. This sign is usually fitted just to the ‘user’ side of each door leaf.

Automatic Fire Door Keep Clear

14 Different Grades of single axis door and window hinges are identified in this important European standard.