SMOKE, HEAT, AND CO DETECTORSLECTURE 21

SMOKE DETECTORS ARE FOUND IN NFPA 72 (NATIONAL FIRE ALARM CODE)

FOR FIRES TO OCCUR, 3 THINGS ARE REQUIRED.1. FUEL2. OXYGEN3. IGNITION SOURCE

O2

FUEL IGN SOURCE

SMOKE DETECTORS SAVE LIVES. MOST FATAL FIRES OCCUR AT NIGHT WHEN PEOPLE ARE ASLEEP. OFTEN, VICTIMS NEVER WAKE UP. A WORKING SMOKE DECTECTOR WILL DETECT SMOKE AND SOUND AN ALARM TO ALERT YOU, GIVING YOU PRECIOUS TIME TO ESCAPE.

TYPES OF SMOKE DETECTORS

BATTERY POWERED

A/C POWERED

A/C WITH BATTERY BACKUP.

A/C WITH BATTERY BACKUP INTERCONNECTED TO OTHER SMOKE DETECTORS.

Interconnecting powered smoke alarms is essential to provide the earliest possible warning of a fire. But hard wired interconnection is expensive, time consuming and disruptive. A hard wired system is also difficult and expensive to reconfigure when circumstances (or standards) change. With RadioLINK, mains powered smoke alarms are interconnected by wireless signals rather than cabling. It's so much simpler, more convenient - and easier to change or extend as and when required.

Wireless Smoke Detector Hidden Camera DVR Spy 4GB

The Smoke Detector Spy Camera will activate only when it detects motion. A wireless remote control allows for control of the Smoke Detector Camera without having to physically touch the Smoke Alarm unit

This Self Contained Smoke Detector Hidden Camera may easily be charged via USB. Built-in 4GB flash memory gives you up to 100 minutes of recording time. Not functional as a smoke detector.

SMOKE DETECTORS FOR THE HEARING INPAIRED WITH FLASHING LIGHTS.

SMOKE DETECTORS MUST BE REPLACED AFTER 10 YEARS

http://www.engineerguy.com/videos/video-smoke.htmHow smoke detectors work

The most commonly used detectors are the ionization detectors and the photoelectric detectors. Ionization detectors are prone to malfunction when used in noisy, dusty, or damp environments and are subject to frequent maintenance. Ionization detectors also produce radiation pollution. Photoelectric detectors detect the intensity of infrared light pulses that are reflected from the smoke in order to deduce the density of the smoke.

TWO TYPES OF SMOKE DETECTORS

1.Ionization2.Photoelectric

Ionization smoke detection is generally more responsive to flaming fires. . Ionization technology is generally for detecting small particles, which tend to be produced in greater amounts by flaming fires, which consume combustible materials rapidly and spread quickly. Sources of these fires may include paper burning in a wastebasket or a grease fire in the kitchen. How they work: Ionization-type smoke alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm.

An Americium container from a smoke detector. Half Life 243 years

IONIZATION TYPE SMOKE DETECTOR

Ionization sensor smoke alarms contain a small amount of radioactive material, americium embedded in a gold foil matrix. The ionization chamber is basically two metal plates a small distance apart. One of the plates carries a positive charge, the other a negative charge. Between the two plates, air molecules-made up mostly of oxygen and nitrogen atoms-are ionized. As they migrate to charged plates In the smoke-free chamber, positive and negative ions create a small current.

Ionization Technology

Smoke particles and combustion gases interact with the ions generated by the alpha particles, restoring them to their neutral electronic state and decreasing the electrical current passing through the cell. As fewer ions are available to migrate to the plates, the disrupted current triggers the alarm

Inside a basic ionization smoke detector. The black, round structure at the right is the ionization chamber. The white, round structure at the upper left is the piezoelectric buzzer that produces the alarm sound.

SECTION VIEW OF AN IONIZATION SMOKE DETECTOR

Photoelectric Smoke Alarm Technology

Smoke particles in chamberdeflect some light rays

Smoke free chamberlight beam travels straight through;

LED

No light reaches photoelectric cell

  Activatedphotocellpowers alarm

Deflected light raysactivate photocell

. Photoelectric technology used in the sensor is generally for detecting large particles, which tend to be produced in greater amounts by smoldering fires, which may smolder for hours before bursting into flame. Sources of these fires may include cigarettes burning on couches or bedding.

How they work: Photoelectric-type alarms aim a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light onto the light sensor; triggering the alarm.

Optical Smoke Detector1: Optical chamber2: Cover3: Case moulding4: Photodiode (detector)5: Infrared LED

OPTICAL SMOKE DETECTOR WITH THE COVER REMOVED.

The A5366CA is a low-current BiCMOS circuit providing all of the required features for a photoelectric type smoke detector. This device can be used in conjunction with an infrared photoelectric chamber to sense scattered light from smoke particles.

* Interconnect Up to 50 Detectors * Piezoelectric Horn Driver * All Internal Low-Battery Detection * Power-ON Reset * Internal Timer and Control for Reduced Sensitivity * Built-In Circuits to Reduce False Triggering * 6 V to 12 V Operating Voltage Range * ESD-Protection Circuitry on All Pins * Temporal Horn Pattern

The RE46C190 is a low power, low voltage CMOS photoelectric type smoke detector IC. With minimal external components, this circuit will provide all the required features for a photoelectric-type smoke detector. The design incorporates a gain-selectable photo amplifier for use with an infrared emitter/detector pair. An internal oscillator strobes power to the smoke detection circuitry every 10 seconds, to keep the standby current to a minimum. If smoke is sensed, the detection rate is increased to verify an Alarm condition. A high gain mode is available for push button chamber testing.

There are several types of flame detector. The optical flame detector is a detector that uses optical sensors to detect flames. There are also ionization flame detectors, which use current flow in the flame to detect flame presence, and thermocouple flame detectors.

FLAME DETECTORS

Ultraviolet (UV) detectors work with wavelengths shorter than 300 nm. These detectors detect fires and explosions within 3–4 milliseconds due to the UV radiation emitted at the instant of their ignition. False alarms can be triggered by UV sources such as lightning, arc welding, radiation, and sunlight. In order to reduce false alarm a time delay of 2-3 seconds is often included in the UV Flame detector design. Near Infrared (IR) array flame detectors, also known as visual flame detectors employ flame recognition technology to confirm fire by analyzing near IR radiation via the pixel array of a charge-coupled device (CCD). Infrared (IR) flame detectors work within the infrared spectral band. Hot gases emit a specific spectral pattern in the infrared region, which can be sensed with a thermal imaging camera (TIC) a type of thermographic camera. False alarms can be caused by other hot surfaces and background thermal radiation in the area as well as blinding from water and solar energy. A typical frequency where single frequency IR flame detector is sensitive is in the 4.4 micrometer range. Typical response time is 3-5 seconds

Be sure to install alarms in the following places.

– Install an alarm inside each bedroom and outside each separate sleeping area. (hallways)

– Install an alarm on each level of the home including the basement.

•Don't place alarms where it is inconvenient or unsafe to test them, like in tall foyers or high over a stairway.

•A smoke alarm installed in a stairwell must be located in such a way that smoke rising in the stairwell cannot be prevented from reaching the alarm by an intervening door or obstruction.

•A smoke alarm installed to detect a fire in the basement must be located close to the stairway leading to the floor above.

AVOID PUTTING SMOKE DETECTORS IN THE FOLLOWING PLACES

There are certain locations to avoid such as near bathrooms, heating appliances, windows, or close to ceiling fans. Don't place smoke detectors in kitchens, bathrooms, furnace rooms, workshops, garages, or in other spaces where temperatures can fall below 32°F, or exceed 100°F. These areas are subject to fumes, steam, dust and smoke, which can generate false alarms and contaminate the alarm. Don't install detectors where air movement can delay the alarm. This means they should be away from windows and at least 3 ft from warm or cold air ducts or return ducts. Also, don't install them between an air return and a bedroom door. Smoke alarms should not be located within 3 ft of doors to a kitchen or bathroom with tub or shower.

SMOKE DETECTORS MUST BE PLACED AT LEAST 3 FEET AWAY FROM HVAC REGISTERS AND CEILING FANS OR INSTALLED PER THE MANUFACTURES INSTRUCTIONS.

3 FEET

INSTALLATION OF SMOKE DETECTORS

KEEP SMOKE DETECTORS OUT OF DEAD SPACES WHERE WALLS MEET THE CEILING

Smoke detectors should be mounted on the ceiling at least 4 inches from a wall or on a wall with the top of the alarm not less than 4 inches, or more than 12 inches, below the ceiling.

DO NOT INSTALL INTHIS AREA.

4”

INSTALL IN THIS AREA.

36” 36”

WHERE TO INSTALL SMOKE/HEAT DETECTORS IN CATHEDRAL CEILINGS

WHERE TO INSTALL SMOKE/HEAT DETECTORS IN SLOPED CEILINGS

36”

4”

DO NOT INSTALL IN THIS AREA.

INSTALL IN THIS AREA.

•If smoke alarms are placed in a room with sloped ceilings, the alarm should be located on the high side of the ceiling.

THESE SMOKE DETECTORS ARE INTERCONNECTED, IF ONE GOES OFF, THEY ALL GO OFF.

HEAT DETECTORS

Heat Detectors respond to fire, not smoke. While Smoke detectors get all the attention, heat detectors are another useful component of any modern fire detection system. Some environments can trigger nuisance alarms in conventional smoke alarms due to shifts in temperature and humidity as well as dust, fumes and insects. Heat detectors are intended for use in locations where standard smoke alarms are not suitable because they are virtually unaffected by these adverse conditions. Heat detectors are useful in Kitchens, Unfinished Attics, Basements, Garages, and other areas where high levels of dust and fumes are present.

DO NOT install heat detectors in areas with high humidity. Also do not install in rooms where temperatures may fall below -10 degrees F or rise above 100 degrees F or near fluorescent lights (electrical noise and flicker).

Rate-of-rise heat detectorsRate of rise detectors may not respond to low energy release rates of slowly developing fires. To detect slowly developing fires combination detectors add a fixed temperature element that will ultimately respond when the fixed temperature element reaches the design threshold.

There are two types of heat detectors. One triggers at a temperature above a certain point, about 58°C. The other type of heat detectors detects the temperature increase within a certain period of time. About 15°C in one minute. Then the alarm will trigger. These heat detectors are able to warn you very much earlier than the fixed temperature heat detectors and also they are useful in cold weather.  

Fixed temperature heat detectorsThis is the most common type of heat detector. Fixed temperature detectors operate when the heat sensitive alloy changes from a solid to a liquid. The most common fixed temperature point for electrically connected heat detectors is 136.4°F (58°C). Technological developments have enabled the perfection of detectors that activate at a temperature of 117°F (47°C), increasing the available reaction time and margin of safety. This type of technology works without the use of batteries or electricity as shown in the picture.

CO alarms have a limited life-span. (3-5 YEARS)

CARBON MONOXIDE DETECTORS

More CO detectors

The new state building code is designed to protect you from carbon monoxide gas, which kills 500 people a year and sickens 20,000 others. It's dubbed the "silent killer." It's colorless, odorless, and tasteless. So unless you actually see visible smoke that often occurs with carbon monoxide, you won't know.

Carbon Monoxide Detectors http://www.youtube.com/watch?v=CAYHMu1F7ww

When CO comes into contact with the circuitry, it lowers the electrical resistance. The processor detects the change and causes the alarm to sound. These sensors require lots of electricity, so they generally plug into wall outlets rather than using batteries.

The CO sensor identifies and measures CO gas concentration in the atmosphere in parts per million (ppm). When the sensor detects dangerous levels of the gas, it sends an electronic pulse to the alarm. The higher the concentration, the faster the alarm will respond. For example, the alarm will respond to concentrations of about 70 ppm in as little as an hour but will respond to concentrations of 400 ppm in as little as four minutes The alarm sounds at about 85 decibels (dB), just a little quieter than a typical lawnmower, but often very shrill.

How to Choose a Carbon Monoxide Detector Location.

SECTION VIEW

FLOOR PLAN VIEW

CO DETECTORS

COMBINATION SMOKE AND CO DETECTOR