Control buildings detection systems

Where it is possible for flammable or toxic gas or vapor released within a hazardous area to migrate to the inlets for HVAC systems serving nonhazardous enclosed areas such as control rooms, detection systems should be installed in those HVAC inlets or connecting ductwork. Detection should be provided in HVAC system intakes if the building, room, or enclosure served is not electrically classified and a flammable (or toxic) gas or vapor could feasibly be drawn into the area, either by mechanical ventilation systems or by differential pressures. The detection system should alarm and automatically shutdown the HVAC to prevent gas or vapor concentration in the protected space from reaching the flammable or toxic range. 

The unmanned compressor building was equipped with a combustible gas detection system. However, it failed to sound an alarm because of a faulty relay in the control room. Automatic fail-safe valves functioned properly, blocking-in the flow of ethylene, but not before 450-11,000 lb of gas had already escaped. 

The liquid level in the 300,000-gal tanks that contain highly radioactive waste is continuously monitored. A level indicator in each tank is set to alarm when the volume reaches 285,000 gal. This alarm sounds in both the control house and the main process building. A second leak detection system is a liquid-level indicator in the sump of the vault surrounding the tanks. 

Active for example, safety shutdown systems to prevent accidents (e.g., a high level alarm in a tank shuts automatic feed valves) or to mitigate the effects of accidents (e.g., a sprinkler system to extinguish a fire in a building). Active systems require detection of a hazardous condition and some kind of action to prevent or mitigate the accident. Multiple active elements involve typically a sensor (detect hazardous condition), a logic device (decide what to do) and a control element (implement action). 

The biosensor and response system used a tiered approach. Samples of airborne biological material were taken continuously by the Joint Biological Point Detection System (JBPDS) equipment, which was not commercially available. Operation of these systems was monitored continuously at a separate control facility. Initial detection by the JBPDS equipment was followed by a second-tier assay analysis that, if positive, would result in physical collection of sampled material for additional analysis off-site. The confirmed second-tier analysis would result in notification of JBPDS leadership and shipment of a sample to the Utah Department of Health for further laboratory analysis. Because the confirmatory test would take 12-24 hours to complete, the primary function of the higher-tiered detection was to define treatment and decontamination responses (LP-3 options). Change in building or HVAC operation on the fifth and sixth floors would not be initiated until the Utah Department of Health analysis confirmed detection of a biological threat agent. 

Greater effort is needed to build management systems that help limit development of resistance to new pesticides as well as to conserve other valuable tactics of pest control, such as pest resistant host plants and even some biological control agents (Croft et al. 1988). Such effort will be required for genetically improved forms of these pest control agents, as well. Effective management systems should be put in place before these new tactics of pest control are deployed rather than after problems of pest adaptation to them are detected in the field. 

Continuous Pu-in-air monitoring is provided for all areas within the building, with alarms both local and repeated in the Health Physics control room. The system is available to initiate automatic area evacuation if widespread air activity is detected. 

In this example a sensor (e.g. an automatic fire detector) is activated by combustion products such as smoke, heat or combustion gases. After activating the control unit (e.g. a fire alarm or detection system), it initiates programmed Controls of Fire Protection Systems (CFPS) or activates other actuators in the building. An actuator is for example a... 

Often a broad-band laser (e.g., a pulsed dye laser without etalons), or a multiline laser (e.g., a CO2 or CO laser without grating) may simultaneously cover several absorption lines of different molecules. In such cases the reflected beam is sent to a polychromator with a diode array or an optical multichannel analyser (Sect.4.5). If a fraction of the laser power Po(w) is imaged onto the upper part of the OMA detector and the transmitted power onto the lower part (Fig. 15.10) electronic difference and ratio recording allows the simultaneous determination of the concentrations Nj of all absorbing species. A retroreflector arrangement is feasible for measurements at low altitudes above ground, where buildings or chimneys can support the construction. Examples are measurements of fluorine concentrations in an aluminum plant [15.55] or the detection of different constituents in the chimney emission of power plants, such as NO and SO components [15. 56]. Often ammonia is added to the exhaust of power stations in order to reduce the amount of emission. In such cases the optimum concentration of NH3 has to be controlled in situ. A recently developed detection system for these purposes has demonstrated its sensitivity and reliability [15.57]. 

Positive, forced-air ventilation should be provided. The air intake should be taken from a safe, vapor-free location at least 10 meters above grade. If hydrogen sulfide, hydrocarbons, or other toxic or hazardous vapors could be drawn in by the air system, a vapor detection system should be provided. This system should alarm personnel in the control building at 20% lower flammable limit (LFL) and start 100% circulation at 60% LFL. 

The development of computer capabiUties in hardware and software, related instmmentation and control, and telecommunication technology represent an opportunity for improvement in safety (see COMPUTER TECHNOLOGY). Plant operators can be provided with a variety of user-friendly diagnostic aids to assist in plant operations and incipient failure detection. Communications can be more rapid and dependable. The safety control systems can be made even more rehable and maintenance-free. Moreover, passive safety features to provide emergency cooling for both the reactor system and the containment building are being developed. 

At all intakes for fresh air or HVAC systems to buildings in an electrically classified area according to the National Electrical Code (NEC) or subject to ingestion of combustible vapors. Especially if they are considered inhabited, critical or of a high value. Typically control rooms, critical electrical switchgear, or main process area power sources are provided with gas detection. 

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