Voltage on the Notification Appliance Circuit

Voltage on the Notification Appliance Circuit (NAC)

Notification Appliance Circuit (NAC) -- Two Conditions

Normally, when the Notification Appliance Circuit (NAC) isn't in trouble, the NAC is in one of two states or conditions: Alarm (making noise and flashing, notifying people of a fire) and Normal (silent and not flashing).

When servicing the fire alarm system, it's the difference between the two conditions that cause problems for the technicians.

Wires from a Notification Appliance Circuit (NAC) are connected plus to +and minus to -. The trouble is that when measuring the voltage polarity on the wires during non-alarm times, the measured polarity is wrong for the horn or strobe.

In May 2004, Underwriters Laboratories (UL) revised UL 1971, standardizing operating current measurements to provide uniformity among manufacturers. They now require strobe operating current to be measured using root mean square (RMS) rather than peak and average values, and surge currents must be maintained within levels that the system power supply can tolerate. The operating current must be measured at the voltage where the current draw is at its maximum. By and large, these requirements have been implemented by the industry. However, confusion is present across the fire industry because current draws can no longer be specified at the nominal operating voltage of the system.

Alarm Condition

To sound the alarm, the fire alarm panel's Notification Appliance Circuit gets people's attention (Notification) using devices like horns, chimes, bells, and strobes (Appliance), and does this by applying power over the building's wiring (Circuit).

Normal - Not Alarm Condition

Then again, under normal circumstances, to supervise the building's wiring, the panel uses a supervision voltage to drive electrical current through the same circuit.

Voltage Powers the Devices

There's a problem with the devices, though; when power is on -- they're turned on, when power is off -- they're turned off. The horns, bells, chimes, and strobes don't have switches, they're really simple devices.

Turning on the voltage turns on the horns and strobes, but voltage is also used to supervise the wiring. Because this is all sent over the same wires, the voltage is always on.

There has to be a way for the devices to tell the difference between the alarm condition, when alarm voltage is applied to their terminals, and the normal condition, when supervision voltage is applied to their terminals.

NAC Voltage Reversal

To solve this problem, the voltage produced by the panel on the NAC isn't just turned on and off. When the NAC in alarm, the voltage is forward; when the NAC is supervising the wiring, the voltage is reversed.

Polarity Sensitive Device

In order to react to this polarity reversal, the horn or strobe has an internal diode, making the device polarity sensitive.

When the voltage is forward (positive voltage applied to the + terminal of the device) the diode conducts and horn or strobe is on; when the voltage is backward (negative voltage applied to the + terminal of the device) the diode blocks the current and the horn or strobe is off.

Polarity Voltage Problems

The problem we have for the technician, though, is under normal circumstances, the polarity of the voltage on the wires of the NAC is backward.

Many times, before connecting the wires to the horn or strobe, installers, technicians, and other people who maintain the fire alarm system use their voltmeter to make sure of the polarity on the circuit. If the device is connected so the measured positive wire goes to the +symbol, the horn or strobe will never work.

At least from the device's point of view, supervision voltage on the NAC becomes the alarm voltage, and alarm voltage on the NAC becomes the supervision voltage.

Supervision voltage on the circuit has weak power that usually isn't enough to turn on the horn or strobe; the device won't turn on even though its internal diode conducts. When the alarm sounds, and the voltage changes to forward in the building wiring (NAC), the horn or strobe sees this forward voltage as backward and the internal diode won't conduct. In other words, the horn or strobe doesn't notify anyone. 

Inspection Repairs
A number of times, I've had to reverse the wiring for the horns and strobes at the first annual inspection because the installers who put in the system didn't understand this voltage reversal, and never tested the horns and strobes to make sure they all worked.

Then the fire inspector, who should have been shown a fully functioning fire alarm system and not be required to troubleshoot the system for the installers, also missed their mistake.

Panel Trouble on the NAC

Unfortunately, most panels and booster power supplies don't supervise for this problem. They supervise the wire itself, but don't show trouble for a miss-wired device; they let an installer or technician connect the horn or strobe backward.

What's even worse, the supervision power isn't enough to activate the device, so false activation won't indicate anything wrong with the wiring to the installer, either.

The miss-wiring issue will not be discovered until either the next inspection, or when there's a fire and that device doesn't sound. This is, of course, unless the horns and strobes are turned on right then and there to test whether they work.

Voltage Reversal on the NAC

It's important to remember that the polarity of the voltage, measured while the fire alarm system is normal, is backward; it is supervision voltage -- not alarm voltage. 

Start with the NAC supply voltage at the minimum voltage allowed by UL under battery back-up. This value is 20.4 volts (15% below 24 VDC), so 24VDC x 0.85 = 20.4 volts.

Total current draw = (Device amps) x (Number of strobes), so Multiply 0.202 amps (for 110 cd) by 5 (number of strobes). That calculation produces 1.010 amps total current draw {(0.202 amps) x (5) = 1.010 amps}.

Total wire resistance = (Resistance per foot of wire) x (Length of circuit), The total resistance of the wire is determined by the amount of resistance per foot for 12 AWG wire (2 ohms per 1000 ft.) for the length of the circuit. In this case, the circuit length is 500 feet (250 ft. times 2, for the supply and return wires). The resistance of the wire is 1 ohm. { (2 ohms/1000 feet) x (500 feet) = 1 ohm}.

Voltage is equal to resistance times current. The voltage drop, due to the five devices, is 1.010 volts (1 ohm times 1.010 amps), Resistance x Current = Voltage, (1 ohm) x (1.010 amps) = 1.010 volts.

End of line voltage = Minimum voltage - device voltage drop, 20.4 volts - 1.010 volts = 19.39 volts.

This is an acceptable condition since the EOL voltage is greater than 16 volts.

Only when the system goes into alarm, to turn on the horns, strobes, chimes, and bells, does the voltage change to become forward. 

NAC is the acronym for Notification Appliance Circuit. Notification: Tells people of a Fire or other Life Threatening Emergency. Appliance: Horns, Strobes, Chimes, Bells, Klaxons, Speakers. Circuit: Physical wire loop carrying power to the Notification Appliances.

This is the circuit that powers the horns, strobes, chimes, and speakers in a building. This is the circuit that notifies the occupants of a fire. Usually, there is more than one NAC circuit from the fire alarm panel.

Remove Battery Trouble on Fire Panel

Remove Battery Trouble on Fire Panel

I got many calls where FACP is under UPS supply, no need battery nut if we do not use battery then panel show Battery Fault trouble. You also observe this. There is a way to connect an FACU Fire Alarm Control Unit without backup batteries and have it remain in the normal condition. This is typically only used if you have a training and or demonstration FACU (only if the system is not an approved life safety system for the site).

The backup battery charger on an FACP, FACU, MNS, RPS, etc. is always looking for 24VDC.  This is how it supervises the backup batteries.  In other words, this is how the fire alarm control unit knows that backup batteries are present.  The same terminals on the charger also put out 24VDC in order to constantly charge the backup batteries so that they are always ready in the event of primary power loss.

Most jurisdictions require 24 hours of standby and 5 minutes of alarm for a horn/strobe system and 24 hours of standby and 15 minutes of alarm for a voice system. A diode rectifier is a simple contraption made up of 4 diodes placed in a specific order.  This will allow you to connect an AC source on one end yet get a DC source out of the opposite. With the use of one simple diode, you can accomplish this feat.  Simply place the Anode (+ Solid Black) side of the diode into the non-resettable positive 24VDC power output on the FACU / FACP.  Now place the Cathode (- Stripe) side of the diode into the positive terminal of the backup battery charger.

How this works:  Think of a diode as a one way gate.  Electrical current can flow through it in only one direction.  So this trick is actually quite simple.  The diode is providing a positive current path from the +24VDC output on the panel FACU / FACP and into the + terminal of the battery charger thus tricking it into believing there are backup batteries in place.  The reason for the diode is very important.  You need to remember that the battery charger puts out 24VDC as well.  With that said, we need to block that power from coming back into the +24VDC output on the FACP / FACU.  Here is a picture to help explain this trick on how to keep an FACP /FACU in the normal condition without backup batteries.

Fire Detector Types and Selection

There are various types of detectors available for fire detection system designers and each type is suitable for a particular use. The type of fire / smoke being detected will determine the choice of detector.  Section 8.14 of SANS 10139 gives a guide on selection criteria and factors to consider when carrying out a design.

Below are the various types of detectors available.

1. Point Smoke Detectors. These detectors utilize one (or both) of two principles below;

a. Ionization Chamber Smoke Detectors. This type detects smoke by change in current flows between electrode when smoke enters the chamber of an ionization detector. This detector is particularly sensitive to smoke containing small particles, such as are produced in rapidly burning flaming fires, but may be less sensitive to the larger particles found in optically dense smoke of similar mass, such as can result from smouldering fires, including those involving polyurethane foam, or overheated PVC.

The ionisation detectors contain a small radioactive element that exists in the detection chamber. This has led to most manufacturers stopping the production of these devices. Stringent procedures need to be followed when disposing of this type of detector, which ends up being a costly process.

b. Optical smoke detectors. This type detects smoke by means of the light scatter principle. When smoke enters the chamber the small LED light source within the detector is deflected towards the receiver to trigger the detector. Optical smoke detectors are sensitive to optically dense smoke, but are less sensitive to the small particles found in clean-burning fires that produce little visible smoke.

2. Multisensor Fire Detectors. This type of detector contains more than one sensor, each of which responds to a different physical and/or chemical characteristic of fire. The purpose of combining sensors in this way is to enhance the performance of the system in detection of fire by means of smoke, heat or CO gasses. These detectors can reduce certain categories of false alarm.

3. Point Heat Detector. There are two types of point heat detectors.

a. The first type is the Rate of Rise heat detector which reacts to abnormally high rates of temperature change and provides the fastest response over a wide range of ambient temperatures. A fixed temperature limit is also incorporated in these detectors.

b. The second type is the Fixed Temperature which reacts to a pre-determined fixed temperature rather than a rate of rise temperature. The fixed type is suitable where sudden large change in temperature is considered normal for example in boiler rooms and kitchens.

4. Linear Heat Detector. This type comes in the form of length of wire or tube. Ideally suitable for cable tunnels, cable trays, transformer bays, etc. there are two types of linear heat detectors:

a. The Non – Integrating type consists of an electric cable with an insulation of fixed melting point which is suspended over the area to be protected. The melting of the insulation when there is a fire causes a short circuit which causes the system go into alarm mode.

Heat detectors are best suited for:

·         applications where detection speed is not a prime consideration or where ambient conditions would not allow the use of a smoke detector

·         fire detection in small, confined spaces where rapidly burning, high heat fires are anticipated

·         Heat detectors have a lower false alarm rate,

b. The Integrating type is similar to the Non-integrating except in this type the insulation does not melt but electrical resistance is temperature dependent. The average temperature is taken over the whole length of wire rather than sections of it.

5. Optical Beam Detector. The optical beam consists of two units, a transmitter and a receiver which can either be two separate units installed at some distance apart or combined into a single unit and a reflector used to reflect the transmitted beam back to the receiver.

Optical beam smoke detectors can prove economical and effective for the protection of large, open plan spaces with relatively high ceilings (e.g. warehouses), particularly if access to point smoke detectors for maintenance could present practical difficulties.

It is, however, essential that they be mounted to solid construction that is unlikely to "flex" as a result of changes in temperature or imposed load, as this can cause mis-alignment of the optical beam and, hence, fault signals or false alarms.

6. Aspirating Detectors. This type comprises of a small pump which draws samples of the room air through holes in the system pipework into a detector element.

This detector is usually up to 100 times more sensitive than that of conventional point and line type detectors. Aspirating smoke detectors are highly sensitive and can detect smoke even before it is visible to the human eye.

7. Flame Detectors. They come in basically two types;

Infra-Red Flame detectors and Ultra-Violet Flame Detectors.

a. Infra-red flame detectors operate by detecting certain frequencies of flicker produced by flaming fires. They are sometimes used to protect very high spaces, such as cathedrals or atria. The detectors do not need to be ceiling mounted; they can be mounted at relatively low levels on walls around a very high protected space, within which only a very large fire could be detected by ceiling mounted heat or smoke detectors.

b. Ultraviolet flame detectors are not generally suitable for this application, since ultraviolet radiation is greatly attenuated by smoke whereas infra-red radiation penetrates smoke well.

8. Carbon Monoxide Detectors. This type of detector goes into an alarm when they sense a certain amount of carbon monoxide in the air over time. Different types of alarms are triggered by different types of sensors.

Carbon monoxide detectors can be immune to certain environmental influences that can result in false alarms from certain smoke detection systems, such as dust, steam and cigarette smoke, while responding to many types of fire appreciably faster than heat detectors.

9. Duct Probe Unit. This detector is designed to be used where standard smoke, heat and flame types cannot be utilised. It detects the presence of smoke or combustion in extract ventilation ducting systems. Operation is similar to aspirating detectors but it does not contain a pump, it operates on the venturi effect in the sampling pipe providing optimum airflow through the smoke detector.

10. Laser Point Smoke detector. Laser point detectors offer increased sensitivity over general purpose optical point smoke detectors at the expense of increased cost per location. They use the same principles as the optical point smoke detectors.

Smoke Detector - Placements

• Attics, provided it is heated and utilized for storage
• Offices, Classrooms, Lecture Halls and Laboratories
• Corridors
• Custodial Closets and Storage Areas
•  Exception:
  • Custodial closets with slop sink or other sinks subject to steam accumulation.
• Electrical Rooms or Vaults
• Elevators
• Mechanical Rooms
• Recycling Areas
• Stairwells
• Trash Rooms

Smoke detectors shall be placed;

• 4” from wall or ceiling, but not greater than 12” from ceiling on the wall
• 4’ from ceiling supply air diffusers or ceiling fans.
• 10’ from wall supply air diffusers
• not > 30’ apart, except as modified in NFPA 72, chapter 17
• on the ceilings, provided that beams on same ceiling project less than 4” down
• larger beam depth must comply with NFPA 72, chapter 17
• in locations with temperature ranges of (> 32° F to < 100°F)
• in locations with relative humidity levels of < 93%
• in locations where the air velocity < 300ft/min

Choice of detector

Selecting the correct detector for the application is based on several factors including:

·         The speed of fire detection required, based on an assessment of fire risk.

·         The nature and quantity of the combustible materials present, including ease of ignition, heat release rate, likely form of combustion (e.g. smouldering or flaming) and propensity for smoke production.

·         Probable rate of fire growth and spread.

·         The nature of the environment (e.g. humidity, temperature, cleanliness, extent of pollutants and nature of work processes).

·         The proposed fire evacuation strategy;

·         The height and geometry of the protected area;

·         The attendance time of the fire service (particularly in the case of Category P systems).

·         Other active and passive fire protection measures present.

·         The susceptibility of contents to heat, smoke and water.

·         The speed of response to fire, and the probable false alarm rates, of different types of fire detector.

Commonly Asked Questions

Q. How often should I change my smoke detector?
A. The NFPA suggests changing your smoke detectors every 10 years.

Q. Are there options for the hearing impaired?
A. Yes. There are smoke detectors that use visual and audible warnings. These use a bright flashing strobe light in conjunction with the horn to warn of danger.

Q. Why is my smoke alarm chirping (or beeping)?
A. This is usually an indication that the battery is dying and needs to be replaced.

Q. Are there distance or square footage requirements for smoke detector installation?
A. A general rule of thumb and most smoke detector manufacturers' instructions state, that smoke detectors should be installed every 30 feet in straight runs, such as a hallway or large rooms without obstructions in the ceiling. Most smoke detectors will cover approximately 900 square feet. Some states may have more stringent requirements for location and distances. It is best to check with the local municipality or fire department for code requirements and also the insurance carrier for the facility may have further requirements.

Q. Which are the preferable addressable Brand of Smoke Detector, Heat Detector, Multisensor Detector, Aspirating Detectors, Beam Detector ?

A. Smoke Detector: Autronica, ESSER, Edwards

Heat Detector: Autronica, ESSER, Edwards

Multisensor Detector: Autronica, ESSER, Edwards

Aspirating Detector: VESDA, FAAST

Beam Detector: System Sensor, Ravel, FireRay.

NFPA 72 - Mixing Speakers and Horns for Fire Alarm

NFPA 72 - Mixing Speakers and Horns for Fire Alarm

Are we Allowed to Mix Voice Evacuation Speakers with Horns for Fire Alarm Occupant Notification?

This is a question that comes up from time to time and a lot of people have mixed feelings.  In a nutshell, the question in a more specific format is as follows: "Am I allowed to install voice evacuation speakers and standard temporal code-3 horns within the same fire alarm system?”  To make things fair, we will consult the Standards of NFPA 72 as well as the Code of the International Fire Code Section 907.

What code and standard sections relate to mixing audible signals for fire alarm evacuation?

Here are a list of codes and standards that dance around the topic:

NFPA 72 2019 Sections

·                     10.10.7 

·                     18.4.1.1

·                     18.4.2.1

International Fire Code 2015

·                     Section 907 "Fire Alarm and Detection Systems"

NFPA 72 2019 Standard Dissection

NFPA 72 2019 - Section 10.10.7 states "Alarm evacuation signals shall be distinctive in sound from other signals and shall comply with section 18.4.2 and their sound shall NOT be used for any other purpose."

NFPA 72 2019 Section 18.4.2.1 States  "Distinctive Evacuation Signal" "To meet the requirements of section 10.10, the alarm audible signal pattern used to notify building occupants of the need to evacuate (leave the building) or relocate (from one area to another) shall be the standard alarm evacuation signal consisting of a three-pulse temporal pattern.  The pattern shall be in accordance with figure 18.4.2.1 and shall consist of the following in this order.

1.             ON phase lasting 0.5 seconds +/- 10%

2.             OFF phase lasting 0.5 seconds +/- 10% for 3 successive "on" periods

3.             OFF phase lasting 1.5 seconds +/- 10%

 

This section in short describes the three-pulse temporal pattern of an audible EVAC signal. This temporal code-3 signal is generated by horns as well as speakers.  Remember with voice evacuation speakers, there is still a requirement to have the temporal code 3 whoops between the voice message.

What Does a Distinctive Signal Really Mean?

When the term "distinctive evacuation signal" is used, it's not meant to cover voice evacuation speakers versus horns or bells but to ensure that a temporal 3-pulse pattern or other approved audible tone is used for fire alarm evacuation and ONLY that.

Example: A 4-wire CO detector tied to the building FA system. If the CO detector activates, its internal sounder will alert nearby occupants of dangerous levels of CO via a temporal code-4 audible output.  These are typically tied to the FA system via a monitor module and activate a non-latching supervisory signal at the FACU. However for the sake of this post, lets say the CO detector activates speakers in the affected area. These speakers would need to produce the same temporal code-4 sound as it is not a fire alarm signal rather a CO alert tone.

A distinctive evacuation signal in the minds of NFPA 72 is simply put, a temporal code 3 or other approved audible tone.  Bottom line is the distinctive signal can ONLY be used for fire alarm evacuation and nothing else. 

What about NFPA 72 2019 Section 18.4.1.1?

Another standard section that trips people up on this topic is NFPA 72 2019 - Section 18.4.1.1.  The standard states "An average ambient sound level greater than 105 dBA shall require the use of a visible notification appliance(s) in accordance with Section 18.5 where the application is public mode or Section 18.6 where the application is private mode."

Section 18.4.1.1 is not so much for horns and speakers but strobes in areas that have an average ambient sound level of 105 dB or greater. The reasons for this is 15 db over average or 105 + 15 = 120 dB (public mode) or 10 dB over average or 105 + 10 = 115 dB (private mode). This violates the Section 18.4.1.2 which sets a limit not exceed 110 dB for the FA audible appliances. 

The language that hits home with this topic is actually found in the Annex.  A.18.4.1.1 states "The code does NOT require that all audible notification appliances within a building be of the same type.  However a mixture of different types of audible notification appliances within a space in not the desired method.  Audible notification appliances that convey similar audible signals are preferred.  For example, a space that uses mechanical horns and bells might not be desirable.  A space that is provided with mechanical horns and electronic horns with similar audible signal output is preferred."

When is Voice Evacuation Required in Place of Horns?

In order to find out WHEN something is required in the world of Fire Alarm, we have to consult a CODE.  Section 907 of the International Fire Code covers "Fire Alarm and Detection Systems".   This is the section where all the fire alarm requirements per occupancy group are broken down.

Some examples of voice evacuation requirements are as follows:

·                     IFC Section 907.2.1.1 Group A occupancies with 1000 or more requires voice evacuation

·                     IFC Section 907.2.3 Exception #2  Group E occupancies with more than 100 persons requires voice evacuation

·                     IFC Section 907.2.13 High-Rise Buildings require voice evacuation.

·                     IBC Chapter 3008 Occupant Evacuation Elevators require voice evacuation

The following is a good example of two separate types of fire alarm occupant notification methods being used for one facility.  Prior to the newer versions of the International Fire Code, it was typical to have Group E occupancies (schools) with horns in corridors, restrooms, classrooms, etc.  However if the auditorium or gym (Group A) has an occupant load of 1000 or more, voice is required. In these cases you would have a standalone voice panel triggered to activate the speakers in the gym/auditorium on general alarm. Currently the 2015 IFC is requiring voice throughout E occupancies if the occupant load is greater than 100 so this is no longer an issue.

To circle back to the original question, "Am I allowed to install voice evacuation speakers and standard temporal code-3 horns within the same fire alarm system?" YES, by code, you are allowed to install different methods of audible tones used for evacuating occupants as long as they have ONE "distinct evacuation signal".  Referencing NFPA 72 2019 A.18.4.1.1, it is not desirable to have different types of audible appliances producing conflicting tones.  This is based on the different audible appliances being installed in one area where they could both be heard at the same time.  For example it would not be desirable to have horns in classrooms and voice evacuation speakers in the common corridor where larger groups of occupants come together.  During an evacuation, the classroom doors would be opened to the corridor and the temporal 3 output from the horns would drown out the speakers thus eliminating any sort of intelligibility.  Even if you provided the correct digital audio file to mirror the horn's temporal sound output through the speakers, the voice portion of the evacuation message would still be played during standard code 3 cycles on the classroom horns. 

Additional VOICE requirements for speakers can be seen in NFPA 72 2019 Section "18.4.1.5".

Ref: NFPA Free login

Fire Doors and Fire Exit Doors

Fire Doors and Fire Exit Doors

A fire door is a door with a fire-resistance rating (sometimes referred to as a fire protection rating for closures) used as part of a passive fire protection system to reduce the spread of fire and smoke between separate compartments of a structure and to enable safe egress from a building or structure or ship.

A fire door is more than just the door itself, it refers to the door, the fixings, the fitting, the ironmongery (latches, handles, etc.) and the frame. Fire doors should be compliant and tested to BS 476 Part 22 or to the European equivalent BS EN 1634-1. BS EN 13502-2, Fire classification of construction products and building elements sets the fire resistance classifications. 

This standard should not be confused with NFPA 80-2019 Standard for Fire Doors and Other Opening Protectives.  NFPA 80-2019 provides guidelines for the installation and maintenance of assemblies and devices used to protect openings in walls, floors, and ceilings whose main goal is to keep fire and smoke from moving throughout a building. Not including fabric fire safety curtains, this standard covers devices that have been the focus of a standardized fire test. Fire doors are designed to stop or slow down the spread of fire, smoke and toxic fumes from one part of a building to another, giving the building's occupants a chance to exit safely. The doors help protect the contents and structure of the building by limiting the fire spread

NFPA 80-2019 addresses information on swinging doors with builders hardware, swinging doors with fire door hardware, horizontally sliding doors, special-purpose horizontally sliding accordion doors or folding doors, vertically sliding fire doors, rolling steel doors, fire shutters, service counter fire doors, and host of others. The document can be used as a means to give guidance to authorities having jurisdiction (AHJs), so they can see if assemblies have met and maintained appropriate standards.

NFPA 80-2019 addresses information on swinging doors with builders hardware, swinging doors with fire door hardware, horizontally sliding doors, special-purpose horizontally sliding accordion doors or folding doors, vertically sliding fire doors, rolling steel doors, fire shutters, service counter fire doors, and host of others. The document can be used as a means to give guidance to authorities having jurisdiction (AHJs), so they can see if assemblies have met and maintained appropriate standards.

Here are some of the key features to look out for in terms of both domestic and commercial use:

•      Fire doors are made up of various components. The door itself is usually made from a solid timber frame, but they can sometimes be covered again in fire-resistant glass.
•      Around the edges of the door will be the intumescent seal, which is designed to expand when temperatures reach beyond 200°C to seal the gaps between the door and frame.
•      For a private premises, it is advised to install fire doors where the risk is most imminent, for example the kitchen, or rooms which house lots of electrical devices. If your property is a new build, it should have been subject to regulations ensuring certain doors are fire doors – check this with the developer.
•           For commercial or non-domestic properties, liability lies with whoever is deemed the ‘responsible person’ for that property or the employer. For example, the owner of the property, or the person in control of the property for trade reasons would be responsible.
•      Thorough risk assessments must be carried out and it is advisable to get professional help with all fire-safety-related regulations. There is more to fire safety than just fire doors; escape routes, lighting, warning systems and equipment checks are also required.
•         When you’re choosing a door it’s important to know what the different specifications mean.
•           Around 42% of deaths during house fires are not from direct contact with the flames, but the consumption of smoke. With this in mind, keep an eye out for a doorset with cold smoke seals. These should be within the intumescent seal.

The same requirements as above will apply to a fire exit door. There are also additional requirements where the door is the final exit point of a building:

1.   The door should open in the direction of evacuation.
2.    There should be no locks or catches. Many use a push bar system that will open the door when pressed down. If the door is also a secure entrance, the lock/catches must self-open when the fire alarm sounds.
3.    The final fire exit door must lead to a place of safety.
4.    It must have a self-closing mechanism so that the door will shut behind people evacuating in order to contain the fire and smoke. This will also limit the oxygen going in to the building which will feed a fire.
5.   The signage will need mandatory fire exit signs that are illuminated. Situated above the door. 

The following requirements must be complied with in respect of premises where necessary (whether due to the features of the premises, the activity carried on there, any hazard present or any other relevant circumstances) in order to safeguard the safety of relevant persons -

a.  Emergency routes and exits must lead as directly as possible to a place of safety;

b.  In the event of danger, it must be possible for persons to evacuate the premises as quickly and as safely as possible;

c.  The number, distribution and dimensions of emergency routes and exits must be adequate having regard to the use, equipment and dimensions of the premises and the maximum number of persons who may be present there at any one time;

d.  Emergency doors must open in the direction of escape;

e.  Sliding or revolving doors must not be used for exits specifically intended as emergency exits;

f.   Emergency doors must not be so locked or fastened that they cannot be easily and immediately opened by any person who may require to use them in an emergency;

g.  Emergency routes and exits must be indicated by signs; and

h.  Emergency routes and exits requiring illumination must be provided with emergency lighting of adequate intensity in the case of failure of their normal lighting.”

The “responsible person” is the landlord, employer, owner, and occupier. Anyone who uses or would require the use of the fire exit will have a responsibility to ensure that it remains clear, free from damage and that any contravention to this is reported to the employer, owner, occupier, landlord as soon as possible.

Sources:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/485420/BR_PDF_AD_B1_2013.pdf
http://firecode.org.uk/Code_of_Practice_hardware_for_fire_and_escape_doors.pdf