Reducing Heat Stress with HVLS Fans
High-volume, low-speed fans help cool off employees and improve efficiency.
- By Dan Anderson
- Mar 01, 2015
Extremely hot weather has always presented problems for industrial facilities, but never more so than today. Excessive heat issues can directly affect an organization's bottom line, causing legal, insurance and regulatory headaches, not to mention lowering employee productivity and morale. With online commerce driving an ever-faster pace of shipping and receiving, monthly average temperatures on the rise, and several high-profile lawsuits in the public’s consciousness (and case law books), facility managers are facing a perfect storm of heat-related issues this summer. Fortunately, there are several ways to address this issue.
Types and Causes of Heat Stress
Heat stress can manifest itself in a variety of forms. While some are less severe than others, all are potentially dangerous. The mildest form are heat fatigue, in which workers begin to lose concentration and perform erratically, and heat rash, which occurs when sweat ducts get plugged and skin becomes agitated and painful. People who've had previous heat rash or extreme sunburns can become more prone to this. Heat stress may also cause heat cramps, typically in the larger muscles used during work, including the back, arms, legs, and abdomen. Dehydration and electrolyte imbalance caused by prolonged sweating are typically its causes.
Heat exhaustion, heat syncope (fainting), and heat stroke are among the most serious types of heat stress disorders. Heat syncope usually happens because of a pooling of blood in the lower extremities and dilated vessels of the skin, leading to low blood pressure and sudden unconsciousness. Heat exhaustion can occur on its own or as a prelude to fainting. Common symptoms are similar to heat fatigue but more severe, including diarrhea, nausea, and disorientation. Heat stroke is the most serious heat stress disorder and can be life-threatening. It occurs when the body's systems of temperature regulation fail and body temperatures rise to critical levels. It can be marked by an absence of sweating, as well as confusion, fainting, and/or convulsions. Hospitalization is a must for anyone who suffers a heat stroke.
Certain types of people are more prone to heat stress than others, including older people, smaller people, and people who exceed standard weight by 15 percent or more. Interestingly, men tend to do better than women in hot, dry heat, but women fare better in extreme humidity. In all cases, fitness is a benefit, while drug and alcohol abuse, high blood pressure, and chronic heart problems or other chronic diseases are a disadvantage. The pace of work is a factor across all categories, as well, because the more energy any worker expends, the more at risk he or she is of a heat stress-related episode.
Factors Affecting Heat Stress Control
Warehouses and loading docks are inherently dangerous and fast-paced environments, so it is particularly important for distribution center managers to be aware of potential heat stress disorders. Unfortunately, most loading docks are not air-conditioned, while most dock staging areas are expansive spaces with tall ceilings, making them hard to cool even if they are air-conditioned. The frequent opening and closing of doors is another added challenge to heat moderation.
Long-term weather patterns and the growth of online retailing are two other factors that exacerbate this problem. Most U.S. states have seen have seen their annual average summer temperatures rise in the last decade, and scientists expect the uptick to continue. The ongoing expansion of online retailing and overnight shipping is another relevant trend because it forces companies such as Amazon to push fulfillment employees to work faster than ever. The fast pace of online retailer operations has had a ripple effect on consumer expectations and shipping norms throughout the logistics industry, causing even non e-tail operations to increase the speed of their operation. Though several of the largest online retailers have faced employee push-back, complaints, and high-profile lawsuits in recent years, there is no reason to think this trend will change.
Higher Temperatures = More Mistakes, Legal Exposure
An uncomfortably hot warehouse and loading dock not only lowers the morale of employees, it can make them less efficient. It's not hard to understand why. As more blood pumps to the skin in an attempt to cool off the body, less blood is available for vital organs including the brain, leading to mental errors. In fact, a study done by NASA concluded that when in-plant temperatures rise to 85 degrees F, worker output drops by 18 percent and errors increase by 40 percent.
While OSHA does not have specific regulations for indoor workplace temperatures, the agency recommends a temperature range between 68 and 76 degrees. Twenty-five states have adopted OSHA-approved plans for compliance with and enforcement of heat illness prevention plans. Failure to comply with these regulations can result in a lawsuit if workers become injured as a result of heat illness.
Addressing Heat Stroke
There are a number of ways facilities managers can address heat stroke issues. From a physical standpoint, water breaks should be encouraged, along with consumption of electrolyte-enhanced sports drinks. Workers moving from a cooler part of the plant or coming back to work after time off should be given time to acclimate to their conditions with unit-output requirements gradually worked back up. Obviously, workers should be moved to a cooler area as soon as they show symptoms of heat stress, and anyone suffering a heat stroke should be taken to the nearest hospital immediately.
From an infrastructure standpoint, there are a number facility upgrades that have an immediate impact, such as using fabric curtain walls to create new, specific air-conditioned areas within a facility without having to cool the entire place. Curtain walls also can be used to enclose heat-generating production equipment. Insulated curtain walls provide up to 40 degrees of temperature separation and can be installed in custom configurations and moved when building needs, or seasons, change. High-speed doors, which can operate at up to 100 inches per second, will also help keep cooled air in and warm air out. Some even snap back onto their tracks after forklift impact, decreasing energy-wasting downtime due to repair or replacement.
How HVLS Fans Help to Control Heat
While adding air-conditioning to a distribution center is the best-case scenario, it isn't always practical due to cost considerations and building configurations. With or without air-conditioning, though, most heat stress-prone warehouses can benefit immensely from high-volume, low-speed (HVLS) fans.
Although smaller, floor-mounted fans can be helpful in a small area, their high wind speed can cause problems and their noisy operating level introduces another other stress-inducing factor. They also use a relatively high amount of electricity. HVLS fans, on the other hand, use relatively little energy and provide a gentle, quiet breeze that is very comforting to workers. According to the U.S. Department of Health and Human Services paper "Workers in Hot Environments," a 2-3 mph air speed creates a cooling sensation of 7-11 degrees F. Air moving faster than 5 mph can be disruptive and provides little, if any, added cooling benefit.
The advantage of HVLS fans is their ability to move large volumes of air and create a steady, light breeze. When the breeze reaches people during the warm months, it creates an evaporative cooling effect and reduces the effective temperature by 10-12 degrees F. To put this in perspective, the effective temperature of an 84-degree warehouse environment can be dropped to 73 degrees by adding a fan moving air at 3 mph. This 11-degree cooling sensation can make workers up to 35 percent more productive.
Technically advanced HVLS fans can move large volumes of air over an area up to 22,000 square feet. A single HVLS fan can replace as many as 10 to 20 floor fans, reducing clutter on the ground and lowering the chances of an accident. By mixing air, HVLS fans also help air-conditioning systems work more efficiently, allowing them to be operated at a lower set point. The breeze from an HVLS fan typically allows up to a 5 degree F increase in the AC system's thermostat setting with no change in employee comfort.
Considerations for HVLS Set-up
There are a number of factors to consider when deciding how and when to use HVLS fans. They include obstructions such as pallet racks, machinery and product staging, personnel work areas, and overall building layout, to name a few. Larger-diameter fans (up to 24 feet in diameter) will move air further down rack aisles and over obstructions. Smaller diameter fans (8-, 10-, and 12-foot fans) can be most effective in specific work areas or where installation space is limited. In recent years, floor-mounted HVLS fans also have become available for use in buildings where overhead obstructions preclude the use of the traditional ceiling-mounted HVLS fans.
Fan suppliers can help configure an array of fans, determining the number, size, and locations that provide the maximum benefit for the investment. They also can offer turnkey installation where on-site resources are not available. While the basic concept is similar across all HVLS fan manufacturers, fan design and performance are key factors to consider. There are significant differences between manufacturers, including the shape and number of blades, blade tilt, hub construction, blade-to-hub connection, and safety features. The performance of different designs will vary in the uniformity of air movement directly below the fan, as well as the height and reach of air movement outward from the fan’s diameter.
Other important considerations include ease of installation, fan controls, local representative support, trial program availability, and warranties.
The use of HVLS fans has gained increased attention as a practical and affordable solution to improving air movement, reducing heat stress, and creating overall better environmental control. These types of fans are now recognized as a valuable supplement to help facility designers and engineers control energy costs and improve employee comfort and productivity. Capitalizing on the advantages of HVLS fans requires careful analysis of each application, as well as each HVLS fan design.
Creating a more comfortable, healthier workplace clearly signals that a company's management is willing to invest in employees and is serious about their safety--as well as the accuracy of the shipments it sends to its customers. All can have a direct and significant impact on the organization's bottom line.
Case Study: HVLS Fans in Action
Indiana and Illinois are infamous for their scorching summer temperatures, and the summer of 2011 was one of the hottest ever. However, for workers at one Illinois-based OEM automobile parts manufacturer, the record-setting heat was a stark contrast to noticeably cooler temperatures inside the plant, thanks to the arrival of three HVLS fans. Designed to move and mix air in large spaces, the fan installation brought down plant temperatures by roughly 6 degrees while allowing the plant's air conditioners to run at decreased capacity. In addition to enjoying a cooler main workspace, the employees of the facility also noticed the air-conditioning in areas of the plant it had never reached before.
According to the plant's maintenance manager, the newly comfortable conditions even motivated workers to be more energy conscious. "Many of our guys had never felt cooler air around the front shipping docks," he said. "Now that they have, they are really careful about shutting doors to keep that cool air in."
The fans at the plant were installed on a Saturday when the plant was closed, a mere three days after they were ordered. Their arrival received so much praise from employees that a nearby "sister" plant in Indiana subsequently installed three 24-foot diameter fans of its own.
This article originally appeared in the March 2015 issue of Occupational Health & Safety.