Food safety and temperature go hand in hand. It takes only a few degrees difference in temperature to cause spoilage—whether it be from bacterial growth due to warm conditions or frost damage due to cold. Temperature also affects humidity, which can wreak havoc on both packaging and on food itself.
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Explore This IssueJune/July 2017
Maintaining proper food storage temperature and humidity can be challenging enough in a home, restaurant, or retail setting. However, in large manufacturing and warehousing facilities, the challenges are compounded by storage and access issues as well as the sheer volume of space involved.
Air Stratification and Distribution
One of the biggest issues in warehouse temperature control is caused simply by the nature of the buildings involved. Many of these facilities are thousands of square feet large with 20- to 30-foot high ceilings. Wherever you have a large, high-ceiling space, air tends to stratify. Warmer air rises and cooler air settles, resulting in horizontal layers of air with differing temperatures. This can pose a number of problems, including:
- Difficulty maintaining consistent storage temperatures;
- The formation of cold downdrafts and/or chimney effect, which can adversely affect workers; and
- Unhealthy air conditions due to stagnant, stratified air—which harbors bacteria, molds, and viruses, as well as fumes from forklifts and other equipment.
HVAC alone is not enough to relieve these problems. What is needed is an effective air distribution system. By circulating air from top to bottom throughout the space, the temperature differential can be reduced to a minimum—along with the problems it causes.
One of the most cost-effective ways to address this issue is through the use of fans. Large, industrial sized high-volume low-speed (HVLS) ceiling fans in particular are especially effective at mixing air in large spaces in an energy-efficient manner, without causing uncomfortable drafts or spots that are too hot or cold.
Shutting the Door on Temperature Loss
Another problem faced by most food storage facilities is temperature loss during access to the structure. Warehouse doors and loading docks are typically quite large and allow correspondingly large amounts of air in and out when they are opened. This can lead to frustration when trying to maintain a stable temperature within the building while transporting goods and materials in and out of the structure.
The challenge is to design doorways to enable easy access for both people and goods while minimizing air exchange. Door design plays a critical role in this endeavor. Ideal door design depends on many factors, including location in the building, the equipment to be used, desired temperatures and temperature differentials, and how often the door will be used throughout the day. Effective designs range from heavily insulated cooler doors to high-speed doors, or even vinyl curtains.
Another strategy that can be very effective, especially where a high degree of access and mobility is desired, is to divide two air spaces with air itself through the use of an air curtain. This consists of one or more blower fans positioned above the opening between two spaces, which directs a stream of air downward. The air current effectively separates the two spaces without impeding entry and exit. This works best when there is little pressure differential between the two spaces.
While specialized air curtains or air doors are commercially available for doorways, it is also possible to create an air curtain effect across a larger space by installing a line of small HVLS fans across the ceiling.
Temperature and humidity are closely related, and any attempts to control temperature in a warehouse situation are sure to affect humidity levels as well. While improper humidity levels can adversely affect any product, maintaining proper humidity levels is especially critical were food storage and handling take place. High humidity can encourage mold growth and degrade the quality of many food items. It can also compromise food packaging. Conversely, some food products, like fresh produce, require high-humidity levels to maintain optimal freshness.