When people think about cold storage, the first things that come to mind is the food industry, dairy products, pharmaceuticals, chemicals, and maybe botanical products. One of the last things that comes to mind is fire and heat. However, even in cold storage the danger posed by fire hazards are abundantly present, and these dangers are a threat to your products and your safety. Even more, the fires that take place in cold storage often results in millions of dollars in damages.
Along with the dangers present, the cold, potentially freezing temperatures of these cold storage facilities present an extreme challenge for designing effective detection and suppression devices that can withstand the harsh conditions. In this article I will explain what fire hazards to watch out for, and how to get your facility protected from these hidden dangers.
Contrary to popular belief, cold storage facilities have an abundance of combustible materials to serve as fuel for a fire. On top of that, there still exists powerful sources of heat in these facilities that can cause ignition. For example, some of the leading causes of fires in cold storage facilities are hot work projects, fork trucks, lifters, electronics, lighting fixtures, and arson. In particular, high-intensity discharge lamps (HID lamps) that can be found in these cold storage warehouses may reach over 800° F in temperature.
The use of cold storage facilities has grown along with an increase in the online grocery sales of perishable goods. Along with this is an increase in fire risk, as there are many combustible hazards that are involved with the shipment of these goods. Firstly, goods such as processed dairy, like butter and cheese, and food coloring are considered combustible class III commodities. Food transport also involves combustible materials like polyurethane and polystyrene foams, which are commonly used as insulators; meal kits, cardboard boxes, and pallets, which are common delivery materials; and ammonia-based refrigeration equipment, which can also present fire concerns.
In addition to the potential ignition sources, the cold temperatures and icing in cold storage facilities continue to present a challenge for fire detection and suppression. Cold storage warehouse temperatures are broad, but typically range between -30° F to 70° F. On the other hand, ultra-low temperature pharmaceutical storage facilities can be as low as -90° F or even lower depending on the facility. At the same time, your typical smoke detector has a temperature range form 32° F to 120° F. This means you must consider smoke detector alternatives in order to protect freezing storage warehouses.
In addition, cold storage facilities may also typically have heavy condensation, water vapor clouds, high airflows, and may be inaccessible for regular installation and maintenance. As a result, smoke can often be diluted and dispersed, making detection difficult when using conventional methods. Moreover, besides the temperature difficulties, a typical smoke detector is also greatly hindered by condensing and high airflow spaces.
A reliable detection solution for cold storage applications are aspirating smoke detector (ASD) systems, such as VESDA. An ASD system will pull air in through sampling tubes, which will then travel through a PVC piping network to a filtered detector. As a result, smoke can be detected regardless of high airflow within the cold storage container. Furthermore, the low temperature is negligible for the actual detector, which will be located in a different location. ASD systems often have extremely fast and accurate detection, which can save you a lot of headache from false alarms and ruined goods.
Costs incurred by false alarms are extremely high in cold storage applications, making an ASD system particularly cost-effective. If a facility reaches freezing temperatures, managing water damage from fire sprinklers is further complicated by the potential formation of ice. For use in cold storage applications, Xtralis has a refrigerated storage sampling kit, which is resistant to blockage from condensation and ice.
Linear heat detectors, such as Protectowire, have become increasingly popular in cold storage applications. These types of detectors can detect fire along their length due to their heat-sensitive polymer cable shielding. When the detector is exposed to heat, this shielding will weaken, and will cause a short circuit between two internal steel conductors. Consequently, an alarm signal will activate after the conductors make contact.
Linear heat detection has some unique caveats due to how they function. To start, they can easily be hidden from view, and they require little maintenance. On the other hand, they struggle to detect small, smoldering fires. Since they require heat to activate, they are subject to thermal lag, or the additional time required for the cable to reach its set temperature threshold.
You can protect facilities above 40° F with wet pipe systems; otherwise, use a dry pipe system for frozen storage facilities. However, even dry pipe systems face challenges in the freezing temperatures of cold storage. Firstly, dry fire sprinkler systems are prone to corrosion, ice plugs and other forms of degradation. As a result, they are often filled with either compressed air or nitrogen to increase their longevity and prevent corrosion. Though in freezer storage, there is little need for concern regarding corrosion, due to the lack of liquid water. As a final note, having a nitrogen generator also prevents the buildup of ice plugs, since nitrogen is an inert gas with an inherently low dew point.
Specifically for freezer storage, having a dry air generator is likely your best option. Using a dry air generator, like the Dry Air Pac from General Air Products can be a cost-effective way to prevent freezer room ice plugs. Not only are these devices far cheaper than nitrogen generators, but they are also freezer room friendly. Since corrosion requires the presence of liquid water, you don’t need to be concerned for corrosion in freezer storage sites. The main issue with these applications are ice plugs, which the dry air generator will also help to mitigate while maintaining a higher pressure than a nitrogen system.
For fire sprinklers, your best options are control mode density area (CMDA) and early suppression fast response (ESFR) sprinklers. ESFR sprinklers are mounted on the ceiling, and use high volumes of water to quickly suppress the fire before it has a chance to spread. These sprinklers work well for large storage warehouses, where you may want to avoid the inconvenience of having an in-rack sprinkler system.
CMDA sprinklers are also an option if you want to slow down the spread of a fire to give fire authorities enough time to react to a disaster. The water flow and pressure sent to these sprinklers are based on density-area curves, which determines how much water is required for a given area. Both ESFR and CMDA sprinklers feature high k-factors, but serve different functions. Consult with a qualified engineer to determine which solution is best for your facility.
Knowing the dangers of having a cold storage facility is crucial to ensure that you are making the right decision when it comes to your protection. It can be hard to balance your budget with protection, especially since these facilities can hold high value resources, such as pharmaceuticals. It is usually a cold storage manager’s goal to have as little downtime as possible to preserve the longevity of perishable goods. Thus, it is common to adopt creative solutions that lower maintenance downtime, such as the use of linear heat detection. Furthermore, the dry, cold environment of cold storage prevents the use of conventional detection and suppression systems like smoke detectors and wet pipe systems. Lastly, make sure you maintain your cold storage detectors and sprinklers often, as icing is prone to form around these detectors, which may result in frequent false alarms or an inability to function effectively.
