Risk Assessment

Readers of this series are certainly familiar with smoke detectors. They are just one of a myriad of detector and sensor types used in the industrial setting. Noting the presence or absence of these detectors and sensors during preplanning sessions can give responders an idea of what they will face in the event of a fire, explosion, leak, or other incident. It’s helpful to be able to identify these detectors on sight, but during preplanning sessions, ask the facility contact to point out the various types of detection systems used. It’s also advisable to review fire protection standards before the preplan is started. That way, you’ll know what should be there. If detectors and sensors are not provided where needed, incidents may be more frequent and more severe than they would be otherwise.

Detectors that will provide insight into what responders can expect and what is expected of responders

Aspirating smoke detectors are like human noses sniffing for smoke and can detect fires in their earliest stages. In some cases, such as a telecommunications center, the initial response might be a repair technician rather than the fire service. The technician might fix a smoldering circuit board before it becomes a fire. These detectors are used to protect high concentrations of value that may be especially susceptible to smoke or water damage. The intent is to get the earliest possible response before a fire can do much damage. Firefighting tactics should emphasize minimizing damage to the greatest extent possible.

Heat detectors in detached buildings that are not equipped with sprinklers indicate that the fire service is expected to control the fire without the assistance of sprinklers. Heat detectors respond to fires that are already well under way. In the time interval between detector activation and water application to the fire with hose streams, the fire could easily require 2½-inch (65 mm) hose lines or pre-connected portable master streams. Such an arrangement is frequently provided when it is not economical to extend sprinklers to detached buildings. Important equipment can still be located inside and the building can pose an exposure risk to onsite and offsite properties.

Flame detectors are used when a flaming fire must be dealt with immediately. Flame detectors can activate fire protection systems at chemical plants, underwing monitors in aircraft hangars, ultra-high speed water spray systems in explosives handing facilities, or shut down ventilation fans over ESFR (Early Suppression Fast Response) sprinkler protected warehouses. A form of flame detector is used to monitor boilers to ensure that the flame has not gone out.

Gas detectors can detect gases that can be flammable, toxic, or pyrophoric. Example gases include hydrogen in battery charging areas, anhydrous ammonia at food processing plants, silane at semiconductor manufacturing plants, hydrogen sulfide at refineries, methane detection in sewage treatment plants, and carbon monoxide in pollution control equipment or coal bunkers. They can shut down processes, start ventilation of the gases, or activate systems to scrub the gases. If a facility is monitoring these gases, there is an obvious concern about their release or buildup. This in turn tells the responder that they need to be prepared for these types of incidents. Local HazMat teams should also have hand held monitors to detect the gases found in these facilities.

Gas detection can also be used to avoid transformer failure by monitoring the condition of the transform oil and its dissolved gases.

Sprinkled water flow alarms can be used to shut down all kinds of processes. It is important that the responder knows what is to be shut down so as not to be surprised by a shutdown and so that they can manually shut down the process if the sprinkler interlock fails. A simple example is the need to shut down high volume low speed fans upon sprinkler activation. These fans can negatively influence sprinkler operation if not shut down. Just this week this author recommended that a sprinkler interlock be used to shut down a 6 kW laser welder.

Knowing how alarms are zoned can give an indication of how long it may take to locate the situation. For example, some linear heat detectors might require searching along thousands of feet of cable to find the incident. Other types pinpoint the exact location of detection along the length of the cable.

Conclusion

The wide variety of examples given above represents only some of the uses of detectors that the fire service usually does not learn about at the fire academy. By knowing what detection is present, you’ll have a better idea of what you might face.

In part two of this article, we will address other types of sensors, such as alignment sensors on conveyor belts. We’ll also address how to prepare for events resulting from the lack of needed detectors and sensors.          

Feel free to contact the author at [email protected]

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