Smoke detector

Not to be confused with Smoke alarm.

A smoke detector is a device that detects smoke. Smoke detectors are typically used as initiating devices on fire alarm systems, although in certain cases they may also operate standalone.

Operation

Smoke detectors require power to operate automatically. For two wire conventional detectors, this means they cannot create a short circuit or they will not function. Instead, upon activation, they have an increase in current flow which the panel will still see as enough to activate, but the detector allows for enough power to keep it and sometimes other detectors active.

Four wire detectors work a bit differently, and more often than not are seen on security systems rather than fire, but it is still good to know. Four wire detectors take in both external power, and the IDC (Zone) wires separately. This means that when the detector activates, it causes a short on the IDC, but still has full operation power.

Intelligent detectors work very differently from conventional detectors. For the most part, these are more of sensors than anything. The panel is constantly getting a reading from the detector, and at a certain chamber value, this will cause an alarm. It's designed to be very simple, but this technology allows modern panels to decide when the detector activates, rather than let the detector decide. This can reduce false alarms.

Furthermore, intelligent detectors are smart enough to know when they need to be cleaned, and will send a trouble to the panel to let the panel know it needs to be cleaned. This again reduces false alarms, as a dirty conventional detector will often just go into alarm.

Coverage types

Beam smoke detectors

Under NFPA 72 section 17.7.3.7.5, a beam smoke detector is considered equivalent to a row of spot-type smoke detectors.

Aspirating smoke detectors

Under NFPA 72 section 17.7.3.6.1.1, each sampling port of an aspirating smoke detector is considered equivalent to a spot-type smoke detector.

Duct smoke detectors

Smoke detectors may be installed inside ducts to control HVAC shutdown.

Open area protection

Open area protection may be provided using spot-type, beam, or aspirating smoke detectors. NFPA 72 section 17.7.3 includes prescriptive requirements for detector spacing, but performance-based alternatives may also be used.

Numerous code requirements and reductions exist for open area protection:

• NFPA 1 section 14.3.1(8)(e)(iii) and NFPA 101 section 7.1.3.2.1(8)(e)(iii) requires smoke detection in certain cases when an exit provides access to a mechanical room.
• NFPA 1 section 14.5.3.4.1(5) and NFPA 101 section 7.1.6.4.1(5) requires elevator lobbies to be provided with smoke detection if the exit access doors are normally locked.
• NFPA 1 section 14.5.6.4(3) and NFPA 101 section 7.2.1.10.4(3) requires smoke detection to cover 75 feet around non-egress revolving doors whose collapsing force exceeds 180 lb.
• NFPA 101 section 11.3.4.5.1.2 requires smoke detection in certain parts of airport traffic control towers, and section 11.3.4.4.1(3) requires additional smoke detection if an airport traffic control tower only has one exit.
• NFPA 101 section 12.3.6(5) allows fire-rated construction to be omitted from corridors and lobbies in new assembly occupancies if the building is fully covered with smoke detection.
• NFPA 101 section 12.4.4.3.4 requires new underground/limited access assembly occupancies more than 30 feet below the discharge level to be covered with smoke detection.
• NFPA 101 sections 12.4.7.5.1.3 and 13.4.7.5.1.3 require smoke detection to be provided above stages in assembly occupancies for the purpose of initiating smoke control.
• NFPA 101 sections 12.4.9.4.1 and 13.4.9.4.1 require special amusement buildings to be provided with smoke detection systems, and sections 12.4.9.4.3 and 13.4.9.4.3 emphasize this requirement for special amusement buildings with low light levels.
• NFPA 101 sections 12.7.5.3.7.1 and 13.7.5.3.7.1 require smoke detection in sufficiently large vehicles and boats on display in museums.
• NFPA 101 sections 12.7.12 and 13.7.12 allow clothing to be stored in corridors of assembly occupancies if smoke detection is provided.
• NFPA 101 sections 14.3.4.2.3.1 and 15.3.4.2.3.1 provide a set of conditions allowing pull stations to be eliminated from educational occupancies, one of which being the presence of smoke detection.
• NFPA 101 sections 14.7.4.2 and 15.7.4.2 allow clothing to be stored in corridors of educational occupancies protected by smoke detection systems.
• NFPA 101 sections 16.3.4.5 and 17.3.4.5 require smoke detection in day care occupancies except single-room occupancies that open directly to the outside. Existing day care occupancies may also omit smoke detection if occupants are capable of self preservation.
• NFPA 101 sections 16.6.3.4.2/16.6.3.4.3 and 17.6.3.4.2/17.6.3.4.3 require corridors serving new day care homes to have smoke detection systems if the corridors belong to other occupancies, unless sufficient smoke alarms are installed.
• NFPA 101 sections 16.7.4.2 and 17.7.4.2 allow clothing to be stored in corridors of day care occupancies protected by smoke detection systems.
• NFPA 101 section 17.2.4.3.2 allows existing day care occupancies to have one of its two exits unprotected by fire rated construction if smoke detection is provided on the discharge level and the level below it.
• NFPA 101 sections 18.2.2.2.5.2, 19.2.2.2.5.2, 20.2.2.2.6, and 21.2.2.26 require smoke detection to be provided in (ambulatory) health care spaces locked against egress for patient safety, unless staff can remotely unlock the doors at a constantly attended location. This requirement does not apply to spaces locked against egress for security.
• NFPA 101 sections 18.2.3.4(5)(g) and 19.2.3.4(5)(g) require smoke detection to be provided in exit corridors of health care occupancies if fixed furniture is installed.
• NFPA 101 sections 18.2.5.6.2 and 19.2.5.6.2 require intervening rooms between patient rooms and exit corridors to have smoke detection.
• NFPA 101 section 18.2.5.7.1.3(C) requires smoke detection in hazardous areas of new health care suites if those areas are not separated from the remainder of the suite.
• NFPA 101 sections 18.2.5.7.2.1(B) and 19.2.5.7.2.1(B) require smoke detection in all patient sleeping rooms that are not provided with constant staff supervision, and sections 18.2.5.7.2.3(C) and 19.2.5.7.2.3(C) require smoke detection in sleeping suites larger than 7500 square feet.
• NFPA 101 sections 18.2.5.7.3.2(B) and 19.2.5.7.3.2(B) require smoke detection in non sleeping patient care suites greater than 12500 square feet.
• NFPA 101 section 18.3.4.5.3 requires new nursing homes to provide smoke detection in either corridors or patient rooms.
• NFPA 101 sections 18.3.6.1(1) and 19.3.6.1(1) state that if a space of a health care occupancy opens to a corridor, then the corridor requires either a smoke detection or quick-response sprinkler system, and the open space requires a smoke detection system if it is not constantly supervised by staff. Sections 18.3.6.1(4) and 19.3.6.1(5) remove the requirement of corridor detection in limited care facilities. The remainder of section 19.3.6.1 includes several other exceptions for existing health care occupancies that do not apply to new health care occupancies.
• NFPA 101 sections 19.1.6.7 and 19.1.6.8 require smoke detection in existing patient rooms with certain unprotected types of construction unless the sprinklers are quick-response.
• NFPA 101 section 19.2.5.7.3.2 requires existing non sleeping patient care suites greater than 10000 square feet to either have sprinkler systems or smoke detection systems.
• NFPA 101 section 19.3.4.5.1 requires corridors of existing limited care facilities to have smoke detection unless the corridors serve patient sleeping rooms that are protected by smoke detection.
• NFPA 101 sections 19.7.5.3 and 19.7.5.5 reduce the flammability restrictions on furniture and mattresses in existing health care occupancies when smoke detection is provided.
• NFPA 101 sections 20.3.7.2(1) and 21.3.7.2(1) require smoke detection in ambulatory health care occupancies where some floors are not separated into multiple smoke compartments.
• NFPA 101 sections 22.3.4.4, 22.4.5.9.2, and 23.3.4.4 require detention/correctional occupancies to be covered with smoke detection, excluding some small sleeping rooms and dormitories.
• NFPA 101 sections 22.4.6.2.3 and 23.4.6.2.3 require lockups in buildings to be provided with smoke detection systems.
• NFPA 101 section 24.3.4.1 requires one- and two-family homes to be provided with either smoke alarms or smoke detection systems.
• NFPA 101 section 28.3.4.5 requires smoke detection in new hotels and dormitories not protected by sprinklers.
• NFPA 101 section 29.3.6.4.3 relaxes some construction requirements of existing hotels and dormitories when the corridors are protected by smoke detection.
• NFPA 101 section 31.3.4.4.2 requires smoke detectors in all common areas of existing apartment buildings utilizing "Option 2."
• NFPA 101 section 32.3.3.4.8 requires new residential board and care occupancies with more than 16 residents to provide smoke detection in corridors, and section 32.2.2.3.3(3) extends this requirement to small facilities where sleeping rooms do not have secondary exits.
• NFPA 101 section 33.3.3.4.7.3 allows smoke alarms to be omitted from existing residential board and care occupancies with more than 16 residents if smoke detection is provided in the corridors, and section 33.3.3.6.1.3 removes the separation requirements from the exits of non-sleeping rooms when smoke detection is provided.
• NFPA 101 section 33.3.3.4.8 requires existing residential board and care occupancies with more than 16 residents to have smoke detection in all enclosed corridors and living areas. The living area smoke detection can be omitted if the building is sprinklered and the occupants are sufficiently capable of evacuating.
• NFPA 101 section 39.2.4.7 requires smoke detection in existing small business occupancies with a single exit.
• IBC sections 403.4.1 and 907.2.13 require smoke detection in high rise buildings.
• IBC section 407.4.4.5 requires sleeping rooms in I-2 care suites to be provided with smoke detection if they are used as exit access for more than 8 beds and care providers are unable to supervise the suites, as well as care suites greater than 7500 square feet.
• IBC section 407.4.4.6.1 requires non sleeping I-2 care suites greater than 12500 square feet to be provided with smoke detection.
• IBC sections 407.9 and 907.2.6.2 require Group I-2 occupancies to provide smoke detection in either sleeping rooms or corridors when the sleeping rooms are permitted to be open to the corridors.
• IBC sections 411.3 and 907.2.12 require smoke detection in special amusement areas.
• IBC sections 412.2.3.1 and 907.2.22 require smoke detection in airport traffic control towers.
• IBC section 903.2 requires equipment areas of sprinklered telecommunication buildings to be provided with smoke detection if they are not provided with sprinklers.
• IBC section 907.2.2.1 requires smoke detection to be provided in ambulatory care occupancies.
• IBC section 907.2.3 allows pull stations to be omitted from Group E occupancies under a certain set of conditions, including the presence of smoke detection in corridors.
• IBC section 907.2.6.1 requires smoke detection in Group I-1 occupancies excluding sleeping areas and kitchens. Condition 1 occupancies may reduce this to corridors and waiting areas open to corridors if they are sprinklered.
• IBC section 907.2.6.3.3 requires smoke detection in Group I-3 occupancies excluding small sprinklered sleeping units.
• IBC section 907.2.8.2 requires smoke detection in interior corridors of Group R-1 occupancies, if such corridors exist.
• IBC section 907.2.9.3 requires smoke detection in Group R-2 university buildings in common areas, laundry rooms, and interior corridors, unless the building does not have interior corridors.
• IBC section 1010.2.14 requires buildings with controlled egress doors to be covered with either sprinkler systems or smoke detection systems.
• IBC section 1010.3.1.2 requires smoke detection to cover 75 feet around revolving doors with breakout forces exceeding 180 lb

Other detector locations

Door closers

Smoke detectors are often installed near fire doors to close the doors in the presence of smoke.

Dwelling units

Smoke detectors are often permitted to be used in place of smoke alarms in dwelling units, provided that they are arranged to provide equivalent functionality. This is typically accomplished by mounting the smoke detector on a sounder base or using a smoke detector with an integral horn.

Elevators

Smoke detectors are often installed around elevators to control elevator recall.

Fire alarm system protection

Smoke detectors are typically installed above the FACP and other critical components of the fire alarm system to increase the likelihood of an alarm being transmitted before the system itself can be damaged by a fire. NFPA 72 section 10.4.5 and IBC/IFC section 907.4.1 require a smoke detector to be installed above every FACP, power supply, and communicator located in an area not continuously occupied, unless ambient conditions prohibit the use of a smoke detector, in which case a heat detector is permitted.

HVAC shutdown

Smoke detectors are often required to be installed inside ducts for HVAC shutdown, but the requirement generally does not apply if smoke detectors are installed for open area protection.