Detectors smoke

Smoke detectors are employed where the type of fire anticipated and equipment protection needs a faster response time than heat detectors. A smoke detector will detect the generation of the invisible and visible products of combustion before temperature changes are sufficient to activate heat detectors. The ability of a smoke detector to sense a fire is dependent on the rise, spread, rate-of-bum, coagulation and air movement of the smoke itself. Where the safety of personnel is a concern, it is crucial to detect a fire incident at its early stages because of the toxic gases, lack of oxygen that may develop, and obscuration of escape routes. Smoke detection systems should be considered when these factors are present. 

Ionization and condensation nuclei detectors alarm at the presence of invisible combustion products. Most industrial ionization smoke detectors are of the dual chamber type. One chamber is a sample chamber the other is a reference chamber. Combustion products enter an outer chamber of an ionization detector and disturb the balance between the ionization chambers and trigger a highly sensitive cold cathode tube that causes the alarm. The ionization of the air in the chambers is caused by a radioactive source. Smoke particles impede the ionization process and trigger the alarm. Condensation nuclei detectors operate on the cloud chamber principle, which allows invisible particles to be detected by optical techniques. They are most effective on Class A fires (ordinary combustibles) and Class C fires (electrical). 

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The fire death rate in the United States is decreasing, dropping from a rate of 76 per million in the 1940s, when most constmction and decorative products were made of natural materials, to 29 per million in the 1980s, by which time, PVC had replaced natural materials in numerous appHcations (189). This downward trend can be attributed in large part to improved building codes and the broader use of sprinkler systems and smoke detectors. However, the increased use of more fire-resistant materials, such as PVC, deserves part of the credit for this improvement. 

SI 1980/953 Radioactive Substances (Smoke Detectors) Exemption Order... 

FIRE SIMULATOR predicts the effects of fire growth in a 1-room, 2-vent compartment with sprinkler and detector. It predicts temperature and smoke properties (Oj/CO/COj concentrations and optical densities), heat transfer through room walls and ceilings, sprinkler/heat and smoke detector activation time, heating history of sprinkler/heat detector links, smoke detector response, sprinkler activation, ceiling jet temperature and velocity history (at specified radius from the flre i, sprinkler suppression rate of fire, time to flashover, post-flashover burning rates and duration, doors and windows which open and close, forced ventilation, post-flashover ventilation-limited combustion, lower flammability limit, smoke emissivity, and generation rates of CO/CO, pro iri i post-flashover. 

Fire and smoke detectors and fire-fighting equipment. 

The client insisted on a test. The smoke detectors worked, and the explosive charge operated, but the cutter did not cut the rupture disc. The explosive charge could not develop enough pressure because the volume between it and the rupture disc was too great. The volume had been increased as the result of a change in design installation of a device for discharging the halon manually. 

Fire Smoke detectors, intumescent coatings/seals... 

Levels, tapes, thermometers, hydrometers, light meters, smoke detectors, audio-sensors. Features such as cradle rails, safety eyes and climbing irons should be incorporated into the design of the building. 

Smoke detector. Most smoke detectors use a tiny amount of a radioactive isotope to produce a current flow that drops off sharply in the presence of smoke particles, emitting an alarm in the process. 

Smoke detectors contain a small amount of americium-241. Its de-... 

Smoke detectors contain small amounts of americium-241. Am-241 decays by emitting a-particles and has a decay constant of 1.51 X 10-3 y 1. If a smoke detector gives off ten disintegrations per second, how many grams of Am-241 are present in the detector ... 

The principle behind the home smoke detector is described on page 516. Americium-241 is present in such detectors. It has a decay constant of 1.51 X 10-3 y 1. You are urged to check the battery in the detector at least once a year. You are, however, never encouraged to check how much Am-241 remains undecayed. Explain why. 

Radioisotopes have important commercial applications. For example, americium-241 is used in smoke detectors. Its role is to ionize any smoke particles, which then allow a current to flow and set off the alarm. Exposure to radiation is also used to sterilize food and inhibit the sprouting of potatoes. Radioisotopes that give off a lot of energy as heat are also used to provide power in remote locations, where refueling of generators is not possible. Unmanned spacecraft, such as Voyager 2, are powered by radiation from plutonium. 

C22-0128. Smoke detectors contain small quantities of Am, which decays by emitting an a particle with... 

Am does it contain (c) If this smoke detector malfunctions when its decay rate falls below 3.5... 

Discharge water and emission from facilities that make americium smoke detectors or gauges or produce plutonium for nuclear weapons may contain americium. These operations are strictly regulated, but you can check local health advisories before consuming fish or other seafood from these waters. Nuclear reactors are not expected to discharge measurable amounts of americium. 

Ionization smoke detectors that contain americium are safe when installed. However, you should not allow your children to play with these detectors and they should be promptly returned to the manufacturer for disposal if they are damaged or no longer being used. 

Smoke detectors containing americium that are inoperable, damaged, or no longer needed should be returned to the supplier for disposal. 

Both the general population and workers may be exposed to 241 Am from the production, distribution, and use of ionization chamber smoke detectors. The NRC investigated exposure relating to this device. Their 1979 report concluded that the sum of doses to the population resulting from production, distribution, use, and disposal of 14 million smoke detectors containing 3 pCi (100 kBq) of 241Am each (over 3 times that presently used) that were distributed in 1978 would result in a collective total body dose of 1,100 person-rem (11 person-Sv)—much lower than that which could potentially result in one cancer death (NRC 1979). Exposure to 241Am could result from improper disposal of smoke detectors. The detector could be broken and then disposed of in a municipal landfill or incinerated. The 241 Am from the broken detector could be consumed by a child. 

Populations with potentially high exposure to 241Am from commercial devices such as ionization chamber smoke detectors might include production workers and firemen attending to fires in production facilities, warehouses where a large number of sources or devices are housed, or homes where a small number of the devices might be used. 

NRC. 1979. Environmental assessment of ionization chamber smoke detectors containing Am-241. U.S. Nuclear Regulatory Commission. Washington, DC. NRC-02-78-045. NUREG/CR-1156. http //www.nrc.gov/. December 13, 2000. 

Rundo J, Fairman WD, Essling M, et al. 1977. Ingestion of241 Am sources intended for domestic smoke detectors Report of a case. Health Phys 33 561-566. 

UIC. 1997. Most smoke detectors contain an artificially produced radioisotope americium-241. Americium-241 is made in nuclear reactors, and is a decay product of plutonium-241. Uranium Information Center. Nuclear Issues Briefing Paper 35. http //www.uic.com.au/nip35.htm. January 27, 2000. 

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