By: Andrew Turchet
What is Aspirated Smoke Detection?
•In its simplest form a smoke detector
•Known as:
•ASD (Aspirated Smoke Detection)
•ASSD (Air Sampling Smoke Detection)
How does ASD work?
ASD technology utilizes collective air
sampling vs. point detection
Sampling pipe
VESDA
LaserPLUS
•A
88
sample of air is collected from multiple
sampling holes
Basic rule of application
Sample Hole
=
•
Areas of coverage and spacing are the
same for both
How does ASD work?
Why use ASD?
•Early warning – achieved thru increased
sensitivity and active air sampling
•Difficult to detect smoke
•Stable performance in adverse
environments
•Access is difficult
Early Warning
•Widest sensitivity range available
•can achieve %obs/ft values a 1000 times
greater than conventional photo-electric
•Active
vs. Passive
•air sampling can capture smoke
•Collective
sampling
•gives the advantage of pulling together
quantities of smoke from many sampling holes.
Collectively early warning notification can be
achieved.
Early Warning Applications
•Telecommunications
•IT / Data Centres
•Semi-conductor Fab
•High Value Storage – museums, galleries,
libraries, archive.
Telecom & Data Centre
•High valued
equipment
•Emergency services
•Critical data storage
•Down-time causes
loss of revenue
•Early warning reduces
the risk from fire
8.2* Automatic Detection Systems.
Automatic detection equipment shall be installed to provide early warning of fire. The equipment
used shall be a listed smoke detection–type system and shall be installed and maintained in
accordance with NFPA 72®, National Fire Alarm Code®.
8.2.1* Automatic detection systems shall be installed in the following locations:
(1)
At the ceiling level throughout the information technology equipment area
(2)
Below the raised floor of the information technology equipment area containing
cables
(3)
Above the suspended ceiling and below the raised floor in the information
technology equipment area where these spaces are used to recirculate air to other parts of
the building
8.2.2 Where interlock and shutdown devices are provided, the electrical power to the
interlocks and shutdown devices shall be supervised by the fire alarm control panel.
8.2.3 The alarms and trouble signals of automatic detection or extinguishing systems shall
be arranged to annunciate at a constantly attended location.
A.8.2 Fire detection and extinguishing systems should be selected after a complete
evaluation of the exposures. The amount of protection provided should be related to the
building construction and contents, equipment construction, business interruption,
exposure, and security need. For amplification of the important need of fire protection, see
Chapter 4.
A.8.2.1 The detection system selection process should evaluate the ambient
environmental conditions in determining the appropriate device, location, and sensitivity. In
high airflow environments, air-sampling detection devices should be considered.
6.8.6.1 General. Facilities containing greater than 232 m2 (2500 ft2) of signal-processing
equipment area shall be provided with a very early warning fire detection (VEWFD) system for
detection and alarm processing in accordance with Chapter 8.
8.4.1.3* Use of VEWFD systems with an alert (pre-alarm) condition shall provide for an initial
response by authorized personnel prior to fire department notification.
8.5.3.1.2 VEWFD Sensor and Port Installation.
8.5.3.1.2.1* Every type of sensor and port installed in an area shall be limited to a maximum
coverage area of 18.6 m2 (200 ft2).
8.5.3.1.2.2* Where two levels (high and low) of ports or sensors are provided, each level shall be
limited to a coverage of 37.2 m2 (400 ft2) or less per port or sensor.
(A) The coverage limitation between high and low levels shall be limited to 18.6 m2 (200 ft2) or
less providing for staggered port or sensor arrangements between each level.
8.5.3.1.2.3* Sensors or ports shall be installed to monitor return air from the space.
(A) Where stand-alone packaged HVAC units are installed, sensors or ports shall be installed
where return air is brought back to the unit.
(B) Sensors or ports shall be installed such that each covers no greater than 0.4 m2 (4 ft2) of the
return air opening.
8.5.3.1.2.6 Maximum transport time from the most remote port to the detection unit of an airsampling system shall not exceed 60 seconds.
•Consequences
of an incipient fire
“95% of all fire damage within facilities housing electronic
equipment is non-thermal”
* US Federal Commission of Communications
•Large
amounts of plastics
in cabling, circuit boards,
etc.
•Smoldering fire releases
harmful corrosive byproducts (HF, HBr, ZCl).
•Can lead to immediate or
unexpected
failure.
Difficult to Detect Smoke
•Large open spaces
•Dilution
•High air change rates and distribute and dilute
smoke
•Background
smoke
•Adjusting for high ambient “non-fire” related
smoke
Difficult to Detect Smoke Applications
•Atriums
•Power generation facilities
•Data Centre
•Water, waste and sewage treatment
facilities
•Industrial – mining, steel mills, petrochemical, wood, pulp and paper
Atriums
Atriums
•Stratification
•Thermal lift
•Dilution
in
large volume
•Smoke
movement by
mechanical
ventilation
Atriums
•Sampling at multiple points
High equipment heat output + High cooling
demand = High air change rates
Air Change Rate Calculation
1. Air change rate needs to be calculated
for all protected areas (i.e. under-floor,
room, above ceiling)
2. Determine volume of all protected
spaces
3. Sum total CFM for the HVAC system
serving the space + fresh air
4. Air Change/Hour = Total CFM x 60min
Volume
Smoke Detector Spacing Based on Air Movement
Min/Changes
1
2
3
4
5
6
7
8
9
10
Changes per Hour
60
30
20
15
12
10
8.6
7.5
6.7
6
m2 spacing ft2 spacing
11.61
125
23.23
250
34.84
375
46.45
500
58.06
625
69.68
750
81.29
875
83.61
900
83.61
900
83.61
900
Access is Difficult
•Remote testing
•Detector and test point can be remotely
located to facilitate maintenance
•Fewer
test points
Applications Where Access is Difficult
•Atriums
•Energized spaces
•Prison Cells
•Confined spaces (crawl, attic)
•Hazardous areas
•Elevator shafts
•Congested ceilings
Last Hole (Test Point)
Air-Sampling Detector
(Test Point)
Atriums
•Testing done at most remote point
Prison Cells
•Sampling is performed in exhaust duct of
cell.
•Testing can be done remotely
Prison Cells
•Sampling point
concealed
behind return air
grill
•Out of site out
of mind
Correctional sampling point alerts when
blocked
Congested Ceiling Spaces
Performing annual inspections can be
difficult
Access to under-floor detectors is difficult
Thank you!
Andrew Turchet
Xtralis (manufacturers of VESDA)
416-580-9139
aturchet@xtralis.com