Smoke detection

Smoke detectors are not designed for the hostile atmosphere of a wet station where they are needed. The construction of conventional smoke and heat detectors will not stand up. A Southern California company developed a photoelectric detector that is mounted outside the plemun and searches for flame through a plastic window. These units did not have a stand-alone listing or approval but are Factory Mutual approved as part of a fixed extinguishing system. These are no longer manufactured. 

The analog detector has been replaced with a multispectral digital detector. It covers several bands. The detector is protected by enclosure in a pol5 ropylene box. 

The other accepted detector is the sampling t) e detector. These differ from conventional sampling duct or HVAC detectors found in office building HVAC systems. They are much more sensitive than the ordinary photoelectric or ionization type detector. These detectors have the capability of detecting smoke obscuration in the range of 0.03-0.003%. These detectors can be very successful as early warning devices when used in the return air plenum of the cleanroom air handling system. They can be set for multiple levels of sensitivity. The first level could sound a pre-alarm and a second level could shut down room recirculation and initiate exhaust. 

These deteetors can also be used on sensitive equipment known for their frequeney of serious ineidents. Ion implanters have had electrical problems with their power supplies overheating, causing a fire. This is eritieal with the new ion implanters which have oil filled transformers. The fire will attack plastic lines used to supply the doping gas to the reactor chamber. This type of detector is sensitive enough to detect the overfieating and prevent the ignition and release materials that would seriously contaminate the eleanroom. 

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Provide safe separation distances Install fixed fire protection and alarms, water sprays (deluge), and/or foam systems activated by flammable gas, flame, and/or smoke detection devices... 

Check for plant integrity/flammable leaks periodically or continuously on-line, as appropriate Install appropriate fire/smoke detection, audible alarms Provide adequate fire suppression systems Deal with mishaps such as spillage immediately... 

The use of automatically closing valves operated from gas-, fire- or smoke-detection systems is not normally required for gas installations. The reasons for this are ... 

Install appropriate fire/smoke detection, audible alarms... 

Smoke detection depending upon absorption of ionizing radiation by smoke particles light scattering by smoke particles light obscuration. 

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. 

Very Early Smoke Detection and Alarm (VESDA)... 

Switchgear and relay rooms are required to have smoke detection per NFPA 850, section 5.8.4 and IEEE 979, section 2.7. The activation of the fire alarm should shut down the air handling system. If the facility is especially critical to the continued hydrocarbon process consideration of a fixed fire protection system should be evaluated. 

Where buildings are provided with an individual fire, gas, or smoke detection system, that system commonly actuates a relay upon alarm and transmits a fire alarm, gas alarm, or trouble alarm signal to the attended location(s). 

Early detection is essential. The placement of detectors inside cabinets can significantly reduce the time to detection. An early warning high sensitivity smoke detector (HSSD) smoke detection system can be used to detect incipient stage fires and allow planned repairs prior to equipment failure. Hence, fire suppression may not be required. 

An approved smoke detection system should be provided throughout the computer equipment room(s) and record storage spaces, with alarms locally and to another constantly attended location. The smoke detection system can be used to actuate the fire protection system. 

Smoke detection systems should be extended to include the areas under raised floors and above suspended ceilings that contain grouped cables or a significant quantity of ungrouped cables. 

If a sprinkler system is installed in a computer room or similar area, provisions must be made to automatically de-energize all electrical power to the room and equipment, except power to lighting, in the event of sprinkler operation. Ensure that de-energizing activity leads to a fail-safe condition. Preferably, this should take place prior to water application to minimize damage to exposed electronic circuits. This can be accomplished automatically by smoke detection systems. Manual activation is tolerable for constantly attended locations. Where automatic sprinklers are installed in areas containing minimal combustibles as described above, a sprinkler density of 0.10 gpm/ft (0.38 Ipm/m ) should be provided. Refer to NPEA 75. 

Johnson, J.E., Smoke detection containing radioactive materials. In Radioactivity in Consumer Products, pp. 134-440. NUREG/CP-0001, 1978. 

An ionization instrument for the analysis of gas has been developed in which the gas passes through a small chamber where it is irradiated by a small radioactive source. For a constant source of radiation, the ions produced in the gas d nd on the flow velocity of the gas and on its temperature, pressure and atomic composition. The dependence of the ionization on the atomic composition is a consequence of the different ionization potentials of the differrat types of atoms of the gas and the different probabilities for electron capture and collision. The ion current is collected on an electrode and measured. This current is a function of the gas pressure and velocity since the higher the pressure, the more ions form, while at higher velocity, the fewer ions are collected as more ions are removed by the gas prior to collection. Such ionization instruments are used in gas chromatographs and other instruments as well as in smoke detection systems (the normal radiation source is Am, usually 40 kBq), where secondary electrons condense on smoke particles, leading to lower mobility for the electrons and a decreased ion current. 

Fire and Smoke Detection Fire detection systems and alarms should be considered in hazardous locations. These include gas, thermal, smoke detectors, thermal detectors, as well as IR/UV flame scanners... 

In particular current, voltage, power, cell voltage, cell temperature, gas monitoring, fill level in gas separators, water pressure, gas pressure, hydrogen detection, fire and smoke detection, process values of cooling circuit. 

Currently no smoke detection devises so detection will be due to smoke/fumes entering the cockpit multiple concurrent avionic failures Crew may take too long to respond Catastrophic TBD TBD TBD - need to provide fire suppression instructions in the Crew Reference Cards as well as warning to land ASAP Open... 

Smoke Detects smoldering Easily contaminated Indoor use... 

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