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Gas, smoke and fire detectors are common residential safety products. Many municipal building codes require smoke or fire detectors in multifamily dwellings, in new construction, and, in some cases, in existing single-family homes.

There are three common types of detectors: thermal, ionization and photoelectric. Thermal detectors are activated by heat; ionization responds to smoke and gas particles from a flaming fire; and photoelectric responds to smoke from a smoldering fire.

Here’s how each of the three kinds of detectors works:

Thermal: These detectors, used primarily by large commercial or industrial firms, sound only when the temperature rises to a certain level. They are not nearly as safe as the ionization and photoelectric types in that the fire must be more intense before the thermal unit will sound.

However, they might be the best choice for an area where smoke or heat is normally present and might trigger a false alarm, such as near a cooking stove.

Ionization: Measures the changes in electric current caused by invisible particles ionized in the heat of combustion. They use a non-harmful radioactive source (Americium 241) to transform the air inside them into a conductor of electric current. A small current passes through this “ionized” air. When smoke particles enter the detector, they impede the flow of current. An alarm is programmed to sound when the current gets too low. Ionization detectors respond particularly well to the “smoke” caused by a flaming fire. Since they require very little power, they are effectively powered by household batteries and can be placed almost anywhere in a house (and will work even during a power failure).

These detectors are typically insensitive to smoke from a smoldering fire. And battery-powered models must have their batteries replaced at periodic intervals.

Photoelectric: Involves a small lamp adjusted to direct a narrow light beam across the detection chamber. Next to this light source, but hidden from direct exposure to the beam, is a light-sensitive photocell. Smoke entering the detection chamber scatters the light beam reflecting it in all directions. Some of this reflected light is picked up by the photocell which, at a preset level, triggers the alarm.

A typical photoelectric detector is relatively sensitive to smoke from a smoldering fire (the greatest cause of death in home fires), but reacts slowly to flaming fires-almost opposite of the ionization model.

Most photoelectric models require connection to an electrical outlet. Light bulbs must be replaced every few years.


The Fire Protection Association recommends detectors in every room in the house. The simplest rule for locating a basic smoke detector is mount it between the bedrooms and the rest of the house, but closer to the bedrooms. It is better, however, to install multiple detectors and put one near each sleeping area. In multilevel homes, install one on each level. The basement ceiling, near the steps, is a good location for extra protection. But for the best protection, locate a detector in each bedroom. Detectors have additional features to help in warning the family of fire danger and to help them escape from the house. Some are equipped with lights and are suggested for halls and stairways and any location leading to doors or windows. The idea is to light the escape route. Others have loud sirens to awaken sleeping persons or extra loud horns for use in homes where there are persons with hearing impairment.

Install each detector on the ceiling or on walls between 6″ and 12″ below the ceiling. Do not put it within 6″ of where the wall and ceiling meet on either surface. This is dead air space with little circulation. Do not mount a detector in front of an air supply or return duct.


Radon is a colorless, odorless, radioactive gas that is formed wherever there is uranium-an element present throughout the earth’s crust. Since it is a gas, radon is mobile and poses little health risk if it makes its way to open air. It dissipates quickly in open areas, but if radon seeps into a house, it can collect in hazardous concentrations.

Inhaling radon or its decay products introduces radioactivity into the body-posing serious health hazards. There is no way to predict radon’s presence or concentration through geological studies. One house can have low radon levels, while another located next to it may have high concentrations.

In many homes, radon measurements are made in the basement, since radon enters from the earth beneath the foundation.

There are several types of detectors capable of conducting radon tests.

Alpha-track devices consist of a small sheet of polycarbonate plastic. Alpha particles that strike the plastic cause microscopic pockmarks. After an exposure period, users mail the detector to a lab. The lab’s count of the pockmarks gives a direct measure of the mean radon concentration.

Other types include electret ion chamber, continuous monitor and charcoal liquid scintillation. A short-term test will take from two to 90 days depending on the detection device chosen. Longer tests-usually with electret or alpha-track detectors-will give a more accurate reading of average radon exposure.

Be sure your radon kits meet the Environmental Protection Agency’s requirements or are state certified. The kit packaging will tell you if it’s EPA certified.

Remember that radon levels can change greatly, and a number of factors, such as frequency of opening and closing windows, can affect radon measurements. In addition, determining if radon is a health threat depends upon factors such as measurable radon levels and the number of hours a day a home is occupied.

You can be reassured that simple measures-such as improving basement ventilation-can eliminate a radon problem. Other solutions used in combination with the above methods include sealing cracks and holes in the foundation and concrete floors; using a fan to keep the house pressurized; and installing a heat-recovery ventilator while using the heated or cooled air being exhausted to warm or cool the incoming air.


Carbon monoxide (CO) is a colorless, odorless, deadly gas that poses a potentially deadly health risk to people. Carbon monoxide can be emitted by gas or oil furnaces, dryers, refrigerators, water and space heaters, fireplaces, wood stoves and gas ranges.

CO poisoning is difficult to diagnose since the symptoms-headaches, nausea, fatigue, dizzy spells-are similar to ailments such as the flu.

Battery-powered CO detectors are available that can detect levels as low as .01 percent, and will operate even in the event of a power failure. They should be placed near the sleeping area, and perhaps also near the home’s heating source. Make sure the CO detectors you purchase have the UL seal, which guarantees the product has passed safety and accuracy tests.


When selling fire extinguishers, you should find out where the extinguisher is likely to be used and what kind of fire may be involved . . . Class A, B, C or D fire.

Class A fires – the most common types . . . ordinary combustibles such as wood, paper, cloth, rubber and many plastics.

Class B fires – flammable liquids, gases and greases.

Class C fires – energized electrical equipment or wiring where the electric non-conductivity of the extinguishing agent is important. However, when the equipment or wiring is de-energized, remaining combustion is Class A or B and extinguishers for those fires may be safely used.

Class D fires – combustible metals such as magnesium, titanium, zirconium, sodium and potassium. You will not often be called upon to supply extinguishers for Class D fires.


The most reliable guide to the fire-killing ability of an extinguisher is the rating assigned it by Underwriters’ Laboratories, Inc., which appears on the equipment nameplate. Size alone is not a satisfactory measure of extinguisher effectiveness.

Each rating consists of one or more numbers and letters. The letter tells the class of fire the extinguishing agent is designed for. The number indicates approximate relative extinguishing potential. For example, an extinguisher rated 4A is capable of putting out twice as much burning material as one rated 2A. (The “A” means Class A.)

The number used for Class B extinguishers also shows the square-foot area of a deep-layer flammable liquid fire which a trained operator can put out. Class C extinguishers have no “C” commercial rating.


Water-type extinguisher – Class A fires. Includes water, antifreeze, soda-acid, wetting agent and loaded-stream extinguishers.

Carbon dioxide extinguisher – Class B and C fires. Has limited range and is affected by draft and wind.

Dry-chemical extinguisher – Class B and C fires. Includes sodium and potassium bicarbonate base agents. Dry-chemical extinguishers marked general-purpose or multipurpose can be used on Class A, B and C fires.

Foam extinguisher – Class A and B fires. Not effective on flammable liquids and gases escaping under pressure.

Halon extinguisher – Recommended for Class B and C fires but not for Class A fires in paper, wood and cloth. Halon extinguishers are lighter, more compact and more effective than carbon dioxide and will not stop an engine from running. Halon is colorless, odorless and will not damage engine parts, electrical systems or other sensitive equipment and leaves no residue.

Halon 1211 is a gas found in small hand extinguishers and pressurized with nitrogen. Halon 1301 is a vapor form, somewhat less toxic and found in fixed commercial and marine applications. Halon extinguishers are the most expensive of the types listed here.

A number of extinguishers are labeled “all purpose” or “multipurpose.” They use a fine powder of ammonium phosphate that is effective against all types of fire. They are a logical choice, but not as efficient at extinguishing as the rated units can be for specific types of fires.


One fire extinguisher is not enough protection for a home. Four would provide good protection in a three-bedroom home with a basement and garage-one near the bedrooms, one for the basement, one for the garage and one for the kitchen.

It is recommended that multipurpose, dry-chemical fire extinguisher units be used throughout a house as protection against all types of fires.

Do not mount a fire extinguisher too close to a place fire might occur. For example: In the kitchen, do not mount it close to the stove. In the basement, the best place is at the top of the stairs unless circumstances demand that it be near a workshop area. You should not risk reaching into a fire or going into a burning area to get a fire extinguisher.

Also use caution to fight only minor fires. In case of a serious blaze, all persons should immediately leave the house. Notify the fire department from a neighbor’s home or an alarm box.


People buy safes to protect documents and valuables from fire and theft. When you sell a home safe, find out what the customer wants to protect. Although some fire safes offer sufficient security for valuables, not all maximum security safes have maximum fire protection.

Fire safes designed for home use should at least provide protection for the contents for up to one-half hour at 1550 degrees F; light commercial safes should provide the same protection for up to two hours.

According to Underwriters Laboratories’ standards, a fire safe should retain an inside temperature below 350 degrees F (the temperature at which paper chars) for an hour or more. This rating also includes requirements that the safe be resistant to rupture or explosion at these temperatures. The fire rating must appear on the safe. The National Fire Prevention Association has found that a fire-rated safe performs four times better than a non-rated safe in a fire.

Security of a safe, beyond its fire protection, comes from a combination of retractable and stationary bolts that prevents the safe door from being removed by knocking off or removing the hinges.

Besides fire-rated safes, there are also fire-rated security chests and files in a variety of sizes with key locks and interior organizational features.

There are several locking mechanisms for safes, the most common being a dial combination of three or four digits with a handle or latch for retracting the bolts.

Additional security can be provided if the safe also has a built-in key lock that functions independently of the dial combination. This kind of safe also permits “key only” access when necessary and provides double-lock security at other times.

Another form of locking mechanism is an electronic digital lock in which the dial combination is replaced by a four-digit, changeable, pushbutton combination. The advantage is faster and easier access to the contents without sacrificing overall security.

In addition to freestanding safes, there are safes that can be mounted in walls or sunk into concrete floors. There are also vault doors that can be installed inside existing closet doors to turn a standard closet into a vault. However, it should be noted that these safes are not fire rated.

Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.