PAUL HAY Capital Projects

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Fire Protection: Physical Requirements, Lightning Protection, Detection & Alarm Systems

Author:          Paul Hay

e-mail:            paul.hay@phcjam.com

profile:           www.linkedin.com/in/phcjam

1.0  INTRODUCTION TO FIRE PROTECTION

1.1        Objectives of fire protection are (a) protection of life, (b) protection of property, and (c) continuation of operation.

1.2       Fire Protection involves (a) fire resistance, (b) lightning protection, (c) fire detection, (d) smoke management and (e) fire suppression.

1.3       Fires can only be sustained if fuel, high temperature and oxygen are all present.

1.4       Structure and contents of a building serve as fuel for fires.

1.5       There are three sources of ignition:

1.5.1   Chemical ignition occurs when volatile substances spontaneously combust under normal temperatures or exposure to open flame;

1.5.2   Electrical ignition occurs when heat is supplied by electrical sources such as arcing or static electricity (e.g. lightning);

1.5.3   Mechanical ignition occurs when heat is produced by friction (e.g. overheating equipment).

1.6       Fires develop in four stages:

1.6.1   At the incipient stage, there is no perception of smoke, flame or appreciable heat;

1.6.2   At the smoldering stage, smoke is visible but there is no flame or appreciable heat;

1.6.3   At the flame stage, appreciable heat is not present;

1.6.4   At the heat stage, smoke, flame and appreciable heat are present.

2.0 THE SITE MUST BE PLANNED TO FACILITATE FIRE PROTECTION

2.1     Unobstructed access must be provided for fire apparatus such as pumpers, ladder trucks and tankers:

2.1.1   Ideally, fire trucks should be able to pull alongside every external wall;

2.1.2   The width of driveways should permit full extension of aerial ladders:

W =     (H - 1.8) Cot α + 1.2                                                                              [2.1]

where,

W =     Distance of far-side of truck from external wall, m

H =      Height to which ladder is to be extended, m

α =       Angle of ladder to roadway (60 deg.> α >80deg.)

2.1.3   Utility poles, wide podiums, outdoor sculptures, fountains, etc. can obstruct the use of aerial ladders;

                        2.1.4   Ordinary fire-fighting apparatus can only extend seven storeys.

2.2       Hydrants should be properly located:

2.2.1   They should be installed 0.6 m - 3 m in from a curb;

2.2.2   They should be located at intersections and be no further than 9 m apart.

2.3       Proper outdoor illumination allows swift location of hydrants.       

2.4       Siamese connections should be within 6m from an hydrant and should be visible and conspicuously marked.

2.5       Proximity to highly flammable surroundings increases the risk of fires:

2.5.1   Firewall construction is a viable option;

2.5.2   Water storage for suppression is another; and

2.5.3   External water sprinklers may be placed adjacent to the building's openings.

2.6       More reliance will have to be made of internal systems when the above are not addressed.

3.0 EGRESS SHOULD BE PLANNED TO FACILITATE FIRE PROTECTION

3.1       Buildings should facilitate evacuation on detection of a fire, until fire-fighters arrive:

3.1.1   At least two exits should be provided;

3.1.2   Means of egress should be provided to theses exits;

3.1.3   Elevators are not means of egress.

3.2       Exit signs must be connected to batteries or emergency power.

3.3       Building Codes specify (a) number of exits required, (b) minimum widths of doorways, (c) minimum width of means of egress, and (d) maximum lengths of means of egress:

3.3.1   Automatic door closures should be used at exit corridors and stairwells;

3.3.2   Distances increase with use of sprinkler systems.

3.4       Building codes also specify the maximum permissible floor area and heights with regard to the building use:

3.4.1   Larger areas need fire walls;

3.4.2   Doors to fire walls may be kept open by door hardware but should close in the event of a fire being detected;

3.4.3   Fire dampers are required in ducts passing through fire walls;

3.4.4   Attention should be paid to vertical openings, as the vertical spread of flame is more important than the horizontal spread.

4.0  BUILDING COMPONENTS MUST BE SELECTED FOR FIRE PROTECTION    

4.1    Building codes specify the fire resistance ratings required for building components depending on the distance from site boundaries or adjacent buildings:

4.1.1   Fire ratings of components are expressed in hours;

4.1.2   Intumescent coatings expand when exposed to fires;

4.1.3   Un-rated and non-combustible materials are allowed in some instances.

4.2     Where sprinkler systems are used, floors should be waterproof and detailed for quick removal of water to facilitate continuity of operation.

5.0 HIGH BUILDINGS HAVE SPECIAL REQUIREMENTS FOR FIRE PROTECTION

5.1     Buildings over 7-storeys high should have electrical generators capable of providing emergency power to (a) fire alarm system, (b) exit and emergency lighting, (c) required ventilation system, (d) fire suppression system, (e) voice communication system and (f) fire elevator.

5.2       High-rise buildings should have at least one elevator connected to emergency power.

5.3       Refuge Areas are required to hold persons unable to evacuate: 

5.3.1   Areas must be able to accommodate all occupants of a floor;

5.3.2   Areas must be adjacent to the escape route; and

5.3.2   Areas must be constructed with materials of high fire resistance ratings.

5.4       Tall structures may have smoke tower stair shafts:

5.4.1   Entrance to stairwell is through a vestibule;

          5.4.2   Pressure differential between (a) stairwell and vestibule, and (b) vestibule and floor area are maintained by separate supply and exhaust fans run on emergency power.

6.0 LIGHTNING PROTECTION IS REQUIRED FOR VULNERABLE BUILDINGS

6.1       The average discharge of lightning is 200 x 10⁶ volts at 30,000 amps:

6.1.1   Cold lightning bolts can shatter and kill but not ignite combustibles;

6.1.2   Hot lightning bolts will ignite combustibles as well as shatter and kill.

6.2       There are four important factors to consider:

6.2.1   Frequency and severity of thunderstorms;

6.2.2   The building's exposure;

6.2.3   Indirect effects, such as losing a water tank; and

6.2.4   The value and nature of the buildings contents.

6.3       Lightning protection involves provision of a continuous metallic path to ground:

6.3.1   Air terminals/Lightning rods shall be spaced no further than 6m on centre around the perimeter of a flat roof, or along the ridge of a pitched roof;

6.3.2   Additional terminals shall be spaced no further than 15 m apart in the middle of large open roofs;

6.3.3   All terminals shall be inter-connected;

6.3.4   The roof perimeter shall be grounded by down leads no further than 30 m apart;

6.3.5   Large metal objects (e.g. VAC units must be bonded to the conductor; and

6.3.6   Smaller metal objects (e.g. roof drains) which are less than 1.8 m from a conductor should also be bonded.

7.0  FIRE DETECTION SYSTEMS GIVE EARLY WARNING OF HAZARD

7.1       Fire alarms operate in three stages: (a) signal initiation, (b) signal processing, and (c) alarm indication.

7.1.1   Signal Initiation can be manual or automatic;

7.1.2   Control equipment, such as Annunciators, process the signal;

7.1.3   An audible, and sometimes visible, alarm is activated.

7.2       Manual fire alarm stations are wall-mounted devices used to activate fire alarms:

7.2.1   Alarm stations and alarms are placed in the path of egress;

7.2.2   Stations can be coded or non-coded:

7.2.2.1            Coded stations make audible alarms that identify the device initiated;

7.2.2.2            Coded stations are recommended when over 10-stations are proposed;

7.2.2.3            Annunciator panels identify where non-coded stations are initiated.

7.3       Smoke Detectors are automatic devices powered by either AC or DC power supply:

7.3.1   Protective wiring or conduits are required if AC power is used;

7.3.2   Smoke and gas inhalation is responsible for 75% of fire-related deaths; and

7.3.3   Fires are responsible for the remaining deaths.

7.4       Five types of smoke detectors are available:

7.4.1   Ionization detectors initiate an alarm when combustion particles are generated at the incipient stage of a fire;

7.4.2   Photo-electric detectors initiate an alarm at the smoldering stage;

7.4.3   Ultra-violet (UV) and Infrared (IR) detectors initiate an alarm at the flame stage:

7.4.3.1            UV detectors are best installed in rooms used to store highly flammable or explosive substances;

7.4.3.2            IR detectors are typically installed in enclosed spaces;

7.4.3.3            The sensitivity of either detector can be adjusted to ignore other sources of UV or IR radiation.

7.4.4   Heat detectors sense temperature and initiate an alarm when the temperature or rise in temperature exceeds a threshold value.

7.5       Care should be exercised in locating smoke detectors to prevent false alarms:

7.5.1   Areas with high humidity or steam (e.g. laundries) should be avoided;

7.5.2   Areas with open flames (e.g. labs) should be avoided;

7.5.3   Areas with exhaust gases (e.g. garages) should be avoided;

7.5.4   Designated smoking areas should be avoided;

7.5.5   Areas that are dust laden should be avoided;

7.5.6   Areas with high air movement (e.g. exit doors) should be avoided.

7.6       Where fires can occur in several stages, different types of detectors can be specified.

7.7       Alarms activate bells, horns, or strobes for swift evacuation:

7.7.1   Coded alarms initially sound an audible code and can be programmed to ring continuously afterwards;

7.7.2   Zone coding is more economical than device coding;

7.7.3   Un-coded alarms ring continuously:

7.7.3.1            Devices can be arranged into zones with annunciator panels;

7.7.3.2            The annunciator will identify the alarm zone.

7.8       Water-flow switches placed on sprinkler piping can initiate a signal to an annunciator.

7.9       Alarm systems are available that can activate smoke removal systems, re-route elevators and activate fire suppression systems.

8.0 FIRE ALARM SYSTEMS SHOULD BE SPECIFIED ACCORDING TO THE BUILDING TYPE

8.1       Small facilities, including residential buildings, should use Local Protective Signaling:

8.1.1   An alarm is only made at the affected premises;

8.1.2   Fire Department is notified manually by occupant, neighbour, or passer-by;

8.2     Public buildings (e.g. schools, government offices, museums, etc.) should use Protective Signaling:

8.2.1   This system is essentially local protective signaling with a direct connection to a municipal fire alarm box;

8.2.2   Alarms are automatically relayed to the Fire Department.

8.3       Private facilities (e.g. shops and offices) which are unoccupied for extended periods of time should use Remote Station Protective Signaling:

8.3.1   This is essentially local protective signaling which automatically dials a pre-selected telephone number;

8.3.2   Alarms are communicated to a remote location that is always manned;

8.3.3   The remote office is responsible for taking further action.  

8.4    Large multi-building facilities (e.g. universities, manufacturing plants, etc.) should use Propriety Protection Signaling:

8.4.1   Alarms are relayed to a central control station on the site manned by personnel associated with the facility;

8.4.2   The control room is generally in a security post or supervisory location such as an Energy Management Department;

8.4.3   Signal transmitted to the control room identifies the exact location or zone within the affected building;

8.4.4   The Fire Department is contacted manually after verification. 

FURTHER READING

            Mechanical and Electrical Equipment for Buildings, 8^th edition, Benjamin Stein, John S. Reynolds, John Wiley & Sons Inc., USA, 1992

Construction Materials & Processes, Don G. Watson, McGrawHill Book Co., USA, 1978;

            Ramsey/Sleeper Architectural Graphic Standards, AIA, Robert T. Packard (ed), John Wiley & Sons Inc., USA, 1981;

Architectural Handbook, Alfred M. Kemper, John Wiley & Sons Inc., USA, 1979

Fire Protection: Smoke Management, Fire Suppression & Continued Operation

PAUL HAY Capital Projects

www.phcjam.com

Smoke Management, Fire Suppression & Continued Operation

Author:            Paul Hay

e-mail:              paul.hay@phcjam.com

profile:             www.linkedin.com/in/phcjam

1.0         SMOKE SHOULD BE MANAGED

1.1       Smoke barriers (i.e. curtain boards) are effective in containing smoke in the early stage of a fire.

            1.1.1   An alarm system should already be in place.

            1.1.2   Fire suppression systems should also be used.

1.2       Dilution is another strategy that can be implemented.

            1.2.1   Fire dampers are used to contain the spread of smoke through A/C ducts.

            1.2.2   Fire-rated doors are used to contain the spread of smoke through corridors, shafts, and like spaces.

                        1.2.2.1            Spaces should be compartmentalized.

                        1.2.2.2            Doors left open for extended periods will not be effective.

            1.2.3   Concealed spaces, such as ceiling spaces, can also paths via which smoke spreads.

                        1.2.3.1            Spaces should be compartmentalized.

                        1.2.3.2            Fire detection and suppression systems can be installed within them.

            1.2.4   During a fire, areas adjacent to the affected zone should be pressurized.

                        1.2.4.1            VAC systems must be coordinated with smoke control requirements.

                        1.2.4.2            VAC systems should control smoke by placing positive pressure in exit corridors, stairwells, refuge areas and service shafts.

1.3       Special exhaust systems can be used.

            1.3.1   During a fire, air should be exhausted from the affected zone.

            1.3.2   On detection of a fire, dampers should close the return air duct and VAC systems should be switched to use only fresh air.

2.0       EXTINGUISHERS MUST SUIT THE FIRE

2.1       Fire extinguishers are available as water-based or non-water based mixtures.

            2.1.1   Water damages most contents.

            2.1.2   Water conducts electricity; and

            2.1.3   Flammable oils float on it and are not extinguished.

2.2       Class A extinguishers use water, water-based, or multipurpose chemical agents.

            2.2.1   They are used to extinguish fires to wood, trash, paper and textiles.

            2.2.2   Class A extinguishers should be no further than 33 m from a hazard.

            2.2.3   Schools, Offices and public buildings are classified as “Light Hazard” occupancy and require a. Class A extinguisher for each 300 m².

            2.2.4   Dry-goods shops and warehouses are classified as “Ordinary Hazard” occupancies requiring a Class A extinguisher for each 150 m².

            2.2.5   Paint shops and like buildings are classified as “Extra Hazard” occupancies and require a Class A extinguisher for each 100 m².

2.3       Class B extinguishers use smothering or flame-interrupting chemicals.

            2.3.1   They use Carbon Dioxide, Sodium and Potassium Bicarbonate dry chemicals, foam or halogenated agents.

            2.3.2   These are especially suited for extinguishing flammable liquids.

            2.3.3   Class B extinguishers should be no further than 15 m from a hazard.

2.4       Other extinguishers should be no further than 9 m from a hazard.

.           2.4.1   Class C extinguishers use non-electrically-conducting chemicals such as Carbon Dioxide, Sodium and Potassium Bicarbonate dry chemicals, or halogenated agents and are used for fires on or adjacent to electrical equipment.

            2.4.2   Class A:B:C is a dry chemical extinguisher using ammonium phosphate agents which, though classified as “multi-purpose”, is not suitable for electrical fires because it leaves a hard residue.

            2.4.3   Class D extinguishers use dry powders such as graphite and sodium chloride and is used for combustible metals.

3.0             WATER-BASED SUPPRESSION IS COMMONLY USED.

3.1       Water storage tanks may be provided for fire protection.

            3.1.1   Overhead supply is very effective.

            3.1.2   Fire storage can also be combined with domestic supply storage to prevent water becoming stale; however

            3.1.3   Provision must be made to prevent depletion by domestic use.

3.2       Wet stand-pipes are intended for use of the buildings occupants not the Fire Department.

            3.2.1   They.are connected to a water supply system at one end and hose connections at each floor up to the roof.

            3.2.2   Risers should provide 200 kPa pressure of water at two outlets for 25 minutes.

            3.2.3   Fire hoses are usually located near or adjacent to stairs.

            3.2.4   Hoses must be long enough to reach the whole building.

            3.2.5   Hoses may be installed in hose cabinets.

3.3       Dry stand-pipes are intended for the use of the Fire Department.

            3.3.1   A siamese connection at the street level permits connection of two pumper trucks at the same time.

            3.3.2   Hose connections are provided at the first floor level up to the roof.

            3.3.3   Electrical fire pumps may be required if the pressure of the public main is insufficient.

3.4       Combination stand-pipes are intended for both the building occupant and the Fire Department.

            3.4.1   Siamese connections are provided at the street level;

            3.4.2   Stand-pipes are also connected to the water supply system.

            3.4.3   Check valves from fire storage tanks close when check valve to the siamese connection opens

3.5       Sprinkler systems are installed to lower temperature

            3.5.1   Storage tanks for sprinklers should provide at least 20 minutes of supply to a quarter of the sprinkler heads, until the Fire Department arrives.

            3.5.2   Sprinklers consist of a horizontal layout of pipes placed near the ceiling having sprinkler heads at regular intervals throughout.

            3.5.3   Sprinkler heads can be (a) upright, (b) pendant or (c) side-wall types.

            3.5.4   Ordinary sprinklers have fusible plugs set to open at high temperature.

                        3.5.4.1            Individual heads are independently activated. 

                        3.5.4.2            Activated heads must be replaced after use;

                        3.5.4.3            The main valve has to be used to turn them off.

            3.5.5   Flow control sprinklers automatically close when temperature reduces.

            3.5.6   Sprinkler heads are spaced 3.6 to 4.5 m apart, depending on the occupancy rating for the building.

            3.5.7   There are four arrangements used for sprinkler system installations:

                        3.5.7.1            The wet pipe system is the most common.

                        3.5.7.2            The dry pipe system is used where there is a risk of water freezing.

                        3.5.7.3            Pre-action systems admit water before sprinkler heads open; and

                        3.5.7.4            Deluge systems activate all sprinkler heads simultaneously in areas where there is a risk of flame spreading rapidly, such as airplane hangars.

4.0   NON-WATER BASED SUPPRESSION SYSTEMS ARE AVAILABLE

4.1       Use of non-water-based suppression systems can be hazardous to human occupation.

            4.1.1   Oxygen is suppressed with use of foam or dry chemicals that cover the fuel.

            4.1.2   Oxygen is displaced with use of Carbon Dioxide and halogenated agents; and

            4.1.3   They may cause dizziness in high concentrations

4.2       Carbon Dioxide systems are often used in localized fire hazard areas, such as over stoves.

4.3       Halon systems are expensive and used to protect valuable areas, such as computer rooms, that would be damaged with use of other extinguishing systems.

            4.3.1   Halon is a CFC gas stored in cylinders that is more dense than air.

            4.3.2   It is more effective at protecting a building’s contents than its structure.

            4.3.3   Halon 301 is widely used on special building applications such as Computer Rooms, Museums, Libraries, Telephone Exchanges, and commercial Kitchens.

5.0         CONTINUITY OF OPERATIONS NEEDS TO BE PLANNED

5.1       Special alarm and suppression systems must be installed for critical areas.

5.2       Ventilation systems must be used to purge smoke after a fire and replace it with fresh air, and

5.3       Provision must be made to quickly drain water used by sprinkler systems.

 

FURTHER READING

            Mechanical and Electrical Equipment for Buildings, 8^th edition, Benjamin Stein, John S. Reynolds, John Wiley & Sons Inc., USA, 1992

Construction Materials & Processes, Don G. Watson, McGraw Hill Book Co., USA, 1978;

            Ramsey/Sleeper Architectural Graphic Standards, A^.I.A., Robert T. Packard (ed), John Wiley & Sons Inc., USA, 1981;

Architectural Handbook, Alfred M. Kemper, John Wiley & Sons Inc., USA, 1979

National Building Code of Jamaica, 2^nd edition, Ministry of Finance and Planning, 1992.

Sizing Air-Conditioning Units

PAUL HAY Capital Projects

www.phcjam.com

Topic:            Sizing Air-Conditioning Units

Author:          Paul Hay

e-mail:            paul.hay@phcjam.com

profile:           www.linkedin.com/in/phcjam

SAMPLE PROBLEM

Assuming negligible infiltration, calculate the size air-conditioning system required for an office building constructed as follows:

Location:            Kingston, Jamaica                           Orientation    = North

Dimensions:        18 m x 18 m x 7.2 m high                Stories            = 2

OTTV_r           = 18.2 W/m²                                      Occupancy    = 10 m²/person

OTTV_w          = 113.8 W/m²                                    Lighting         = 15 W/m²

Misc. Power   = 25 W/m²

SOLUTION

(A)         For internal heat-gain,

Total floor area                                 = 2 (18 x 18)            = 648 m²

No. occupants                                  = 648/10                  = 65 persons (approx)

Heat from occupants    = 100 x No. occupants                                                           [1.1]

= 100 x 65   =  6,500 W

Heat from lighting                                = 15 x 648             =  9,720 W

Heat from power                                 = 25 x 648            = 16,200 W

Internal heat-gain                                 =                              32,420 W

(B)         For external heat-gain,

Roof  area                                           = 18 x 18       

                                                           = 324 m²

Heat-gain from roof                             = 18.2 x 324         =   5,896.8 W

Total wall area              = 4 (18 x 7.2)  = 518.4 m²

Heat from walls            = 113.8 x 518.4                           =  58,993.92 W

External heat-gain         =                                                      64,890.72 W

(C)         For A/C size,

Total heat-gain              = 32,420 + 64,890.72                =  97,310.72 W

A/C size                       = Total heat-gain                                                                      [1.2]

   3,516.85 W/Tr

= 97,310.72                               = 27.67           =  30 T (approx.)

   3,516.85