SMOKE DETECTOR – A fire detector designed to operate

when the concentration of airborne combustion products

exceed a predetermined level.

SMOKE DETECTOR SENSITIVITY – The relative degree of

response of a smoke detector expressed in %/foot

obscuration. A high sensitivity detector responds to a lower

concentration of smoke while a low sensitivity detector

responds to a high concentration of smoke under identical

fire test conditions.

OBSCURATION – The unit of measurement where smoke

has an effect on visibility. Expressed in %/foot.

Ionization

First type (Invented in 1941’s by Swiss physicist

Walter Jaeger ,Dr. Ernst Meili)

Best at detecting:

Incipient stage (invisibly small particles)

Fast flaming fires (smaller particle size - 0.01-0.4

micron range)

Dark or Black smoke

Photoelectric

Later technology

Best at detecting:

Slow smouldering fires (larger particle size - 0.4-

10.0 micron range)

Light coloured white/grey smoke

Radio active material -

(Americium-241)

Ionization Chamber and

reference chamber

Electrical Source

Positive and Negative plates

The radio active material

generates ‘Alpha’ particles,

which ‘Ionize’ (“to knock an

electron off of”) the air in the

chamber. The free electron

(negative charge) and the

atom with a missing electron

(positive charge) are attracted

to the oppositely charged

metal plates. The detector

senses a small electrical

current between these two

plates.

Smoke particles entering

the chamber attach to the

ions reducing the current flow.

The detector senses the drop

in current between the plates

and triggers the alarm.

Light Source

Lens to collimate light into a

beam

Photoelectric Sensor

Smoke particles entering the

dark Chamber, ‘Scatters’ light

directing it to the sensor cell,

which increases the voltage

generated by the cell.

Increase in voltage triggers

the alarm.

Optical Smoke Detector

1: Optical chamber

2: Cover

3: Case moulding

4: Photodiode (detector)

5: Infrared LED

Smoke detectors where installed properly and maintained

within their listed sensitivity ranges have proven to be

effective in saving lives and property.

However, smoke detectors become less reliable with time,

due to aging of their electronic components and

environmental conditions, making it even more important to

test the detectors in accordance with the CAN/UL-S536-04

” Inspection and Testing of Fire Alarm Systems”.

Detector sensitivity

after 4 years field exploration

Sensitivity [%/m]

# D

ete

cto

rs

Production

limits

Detector sensitivity

after revision process

Sensitivity [%/m]

# D

ete

cto

rs

Production

limits

10 – 30%

out of the limits

Optical components

after 4 years field exploration

Optical components

after revision process

NIST 2008,

•The Smoke Detector Operability Survey:

“Engineering Laboratory Analysis found that there was a

correlation between the occurrence of

nuisance alarms and the sensitivity of the alarm”,

FIRE INCIDENT STUDY NATIONAL SMOKE DETECTOR

PROJECT 1995:

“U.S. EXPERIENCE WITH SMOKE ALARMS AND OTHER

FIRE DETECTION/ALARM EQUIPMENT 2007”

“Nuisance alarms were the leading cause of disabled

alarms”.

“Problems associated with smoke alarm age may

include “sensitivity drift,” which refers to a shift in the range

of visibility obscuration or particulate density that will activate

the smoke alarm. Such a shift can mean either an

increase in nuisance activations (if sensitivity increases) or a

decreased ability to react promptly to real fires (if sensitivity

decreases)”.

“Since 1997, U.S. fire departments have responded to

more false alarms than real fires”.

“More than one-third of New Zealand households in a

smoke alarm installation program had problems with

nuisance alarms”.

SMOKE ALARMS IN U.S. HOME FIRES – NFPA MARTY

AHRENS 2009

“Foreign objects such as dust, dirt or insects can increase

sensitivity, as can fire products”.

“NIST study found that accumulation of cigarette smoke

could trigger smoke alarms”.

ALBERTA FIRE CODE 2006:

6.3.1.2. Inspection and Testing

1) Fire alarm systems shall be inspected and

tested in conformance with CAN/ULC-S-536, “Inspection

and Testing of Fire Alarm Systems.”

Testing Evolution - CAN/ULC-S536-82

4.4.1 A – Every reasonable effort shall be made to test all components

required in this subsection. In the event that some components cannot

reasonable be made accessible, a list of such components and their

location shall be included in the report. However, all such components

shall be tested at least once every three years.

4.4 – Yearly Testing

4.4.1 Every year the following tests shall be conducted and if a fault is

established appropriate corrective action shall be taken:

F – Each automatic alarm initiating device shall be tested for its

intended function in accordance with the manufacturer’s instructions;

Testing Evolution - CAN/ULC-S536-86

NOTE: A cleaning schedule for smoke detectors, based on the

environmental conditions prevailing and the results of clause 5.3.6.6,

should be established and maintained.

5.3.6.5 Inspect and test the smoke detectors in accordance with the

manufacturer’s recommendations.

5.3.6.6 Smoke detectors shall be tested for operability and the

required sensitivity.

Testing Evolution - CAN/ULC-S536-97

6.6.4 – Smoke Detectors

6.6.4.1.1 – Each smoke detector shall be visually inspected for

cleanliness. Where required, cleaning shall be in accordance with the

manufacturer’s recommendations.

6.6.4.1.2 – Each smoke detector sensitivity value shall be tested to

confirm that it is within its rated operating range, using the

manufacturer’s recommended test equipment.

6.6.4.1.3 – Each smoke detector whose sensitivity is not within the

required operating range shall be cleaned, retested in accordance with

clause 6.6.4.1.2 and if still not within its rated sensitivity, replaced with

compatible smoke detector.

6.6.4.1.5 – Each smoke detector shall be tested for operation by

introducing smoke or simulated smoke to the detector chamber.

5.7.4.1.3 Each smoke detector shall be tested to confirm that it is

within its rated operating range using a test method described in Clause

5.7.4.1.6. (Refer to Appendix E3.1, Field Device Testing-Legends and

Notes.)

Testing Evolution - CAN/ULC-S536-04

5.7.4 Smoke Detectors

5.7.4.1.1 Each smoke detector shall be visually inspected for

cleanliness. When required, cleaning shall be in accordance with the

manufacturer’s recommendations.

5.7.4.1.2 Each smoke detector shall be tested for operation by

introducing smoke or simulated smoke to the detecting chamber in

accordance with the manufacturer’s instructions.

5.7.4.1.4 A smoke detector whose sensitivity is not within the

required operating range shall be cleaned, retested in accordance with

Clause 5.7.4.1.3, and if still not within its rated sensitivity, replaced with a

compatible smoke detector. (Refer to Appendix E3.1, Field Device Testing-

Legends and Notes.)

5.7.4.1.6 Acceptable methods of determining the smoke detector

sensitivity are:

A Manufacturer’s recommended test instrument, equipment, or

method;

B Installed control units or transponders designed to test the

sensitivity of individual smoke detectors; or

C Calibrated instruments that provide the operation as described in

CAN/ULC-S529, Standard for Smoke Detectors for Fire Alarm

Systems, for the purpose of testing smoke detector sensitivity.

Testing Evolution - CAN/ULC-S536-04

5.7.4.1.5 Each smoke detector sensitivity measurement and if

applicable, the cleaning date shall be recorded on the individual device

record. (Refer to Appendix E3.1, Field Device Testing-Legends and

Notes.)

Allowable smoke detector sensitivity is established by

Underwriters Laboratories Canada (ULC) and have their

performance verified by Fire Tests.

All smoke detectors are required

to respond to the same Test Fires.

Nearly all smoke detectors installed in Canada are by:

•EDWARDS SYSTEMS TECHNOLOGIES (EST)

•SIMPLEX-GRINNELL

•SIEMENS BUILDING TECHNOLGIES

•SYSTEM SENSOR

Why test detector function and sensitivity?

Detector sensitivity can, and does, drift. Over-sensitivity

leads to false alarms, under-sensitivity to late alarms - or no

alarms. The need for functional testing through introducing a

smoke type stimulus is well recognised:

“Since stimulus of the sensing element through introduction

of the phenomena or surrogate phenomena which the

detectors are designed to detect forms part of the test(s),

use of a test button or a test magnet (for example) or

compliance with 45(i) (confirmation of analogue values) does

not satisfy the recommendations..”

BS 5839 1: 2002 45.3 (Note 4)

“The detectors shall be tested in place to ensure smoke

entry into the sensing chamber and an alarm response.

Testing with smoke or listed aerosol...shall be permitted as

acceptable test methods...”

USA NFPA 72 2000 Table 10.4.2.2 13.g.1 “Each smoke detector shall be tested for operation by

introducing smoke or simulated smoke into the detecting

chamber...”

CAN/ULC - S-536-04, 5.7.4.1.2

But the requirement for sensitivity checks is also clear in

national standards:

“....tests shall be performed to ensure that each smoke

detector is within its listed and marked sensitivity range...”

USA NFPA 72 2000 Table 10.4.2.2 13.g.1

“....each detector shall be tested to confirm that it is within its

rated operating range...”

CAN/ULC - S536-04, 5.7.4.1.3

Soiling Level vs. Sensitivity Level

Contrary to North America, the European approach is to evaluate

the level of soiling in the detector, which is nothing more than the

inverse of testing remaining sensitivity

Standard = DIN 14675/A1 + VDE 0833-1

DIN 14675/A1:2006 Paragraph 11.5.3 (see notes)

Fire detectors are to be exchanged or overhauled according to the

manufacturer’s specifications. This must be documented in the

operation log book.

w/o Drift Compensation – test with gas every year and replace

on failure or after 5 years with new or factory refurbished unit.

with Drift Compensation – test with gas every year and replace

on failure or after 8 years with new or factory refurbished unit.

Non-monitored – test with gas every year and replace on failure

or after 6 years with new or factory refurbished unit.

Monitored – test with gas every year and replace on failure or

after 8 years with new or factory refurbished unit.

Standard = NF / CNPP

Non-monitored or Monitored – test with gas every year and

replace on failure or after 4 years with new or factory refurbished

unit.

Standard = BS 5839 Part 1

Non-monitored or Monitored – test with gas and measure

sensitivity every year replace on failure with new unit. Testing can

involve using complex testing equipment, whereby the detector is

exposed to a defined smoke concentration. The concentration is

slowly increased, until the device goes into alarm, thereby

establishing the sensitivity.

Testing must in some cases even be witnessed!

Non-monitored or Monitored – test with gas and measure

sensitivity every year replace on failure with new unit.

KNOWLEDGE

Education limited within Alberta

Information can be difficult to source

EQUIPMENT

Specialized

COST

Increases time required when done in conformance with

CAN/ULC Standards.

NEWER SMOKE DETECTORS

Addressable: real time monitoring/diagnostics reporting

directly to the fire alarm control panel.

Some detectors look for fire signature, not just smoke, can

require specialized knowledge to test correctly.

Can utilize drift compensation technology

Conventional: easier testing with information available.

Variety of methods:

Obscuration

Voltage

Diagnostic LED’S

Can utilize drift compensation technology

OLDER SMOKE DETECTORS

Conventional: Information may be difficult to source.

Specialized testing equipment required.

Continued testing with smoke or aerosol over time or incorrectly

used may contribute to detectors either becoming more or less

sensitive over time.

NUISANCE /FALSE ALARMS

DELAYED ALARM SIGNAL

NO ALARM SIGNAL AT ALL

Require better education for those qualified under the AFC, IE

CFAA Fire Alarm Technology Program.

Require fire alarm Testing and Inspections in conformance with the

CAN/ULC-S536-04 ‘Inspection and Testing of Fire Alarm Systems’.

Including smoke detector sensitivity testing,

Where smoke detector sensitivity testing is not done in

conformance with Clause 5.7.4.1.6. A – C, that smoke detector

shall be replaced with a new smoke detector within 5 years.

WHY?

Smoke detectors do drift outside of their listed smoke detector

sensitivity range, introducing smoke into the chamber and seeing

the detector alarm, does not prove that it is still operating within it’s

designed parameters and will work in a real fire condition to detect

the products of combustion when required!

QUESTIONS?