Reducing Heat Stress with HVLS Fans and Dock Seals

Dock equipment keeps conditioned air inside. HVLS fans circulate air to boost employee comfort, safety, and efficiency.

• By Andy Olson
• Mar 01, 2018

Hot and humid weather during the summer months can present major challenges for industrial facilities. 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, rising average temperatures and a myriad of other reasons, facility managers are facing a perfect storm of heat-related issues this summer.

Fortunately, there are several ways to address this problem—from proper loading dock seals and shelters preventing conditioned air from escaping a facility to the use of high-volume, low-speed (HVLS) fans to circulate air within facilities. Before getting into these solutions, it's important to understand the types of heat stress that exist, the issues that stem from heat stress, and steps to take if an employee is suffering from heat stress.

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 forms 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. Heat stress may also cause heat cramps in 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 can also include diarrhea, nausea, and disorientation. Heat stroke is the most serious heat stress disorder. It occurs when the body’s systems of temperature regulation fail and body temperatures rise to potentially fatal 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.

Challenges in Heat Stress Control
Warehouses and loading docks are inherently fast-paced and dangerous environments. Unfortunately, most loading docks are not air-conditioned and most dock staging areas have 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 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 e-commerce companies to push fulfillment employees to work faster than ever.

Higher Temperatures = More Mistakes, Legal Exposure
An uncomfortably hot facility not only lowers employee morale, it makes employees less efficient. As more blood pumps to the skin in an attempt to cool off the body, less blood is available for vital organs such as 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-eight 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 that facilities can address heat stroke issues. From a physical standpoint, water breaks should be encouraged and workers who haven't worked in these types of environments should be given time to acclimate. Obviously, anyone who displays heat stress symptoms should be moved to a cooler area, and anyone suffering a heat stroke immediately taken to the nearest hospital.

From an infrastructure standpoint, there are a number of facility upgrades that can have an immediate impact, such as upgrading dock seals and shelters at the loading dock to create a complete seal around the dock opening and using HVLS fans to circulate air.

Heating Up and Losing Energy (and Money) at the Loading Dock
The loading dock presents the greatest opportunity for the loss of temperature control and energy. Any opening can allow conditioned air to leave and outdoor humidity and foreign contaminants to enter.

Even when trailers are at the loading dock, gaps often exist between the trailer and the edges of the dock opening. Swing-open trailer doors usually lead to 1- to 2-inch gaps. While that might seem insignificant at first glance, it equates to a 2.5-square-foot hole at just one dock opening. That's a lot of cool air escaping and/or hot air infiltrating a facility. Not to mention, depending on the climate of the facility, this represents anywhere from $600 to $1,200 quite literally flying out the door every year. Now, extrapolate those figures over multiple dock doors, and the financial loss is significantly more profound.

But the sides of the dock opening aren't the only gaps in the building's perimeter. Many facility managers forget about the "fourth side" of the dock—the bottom end, where the leveler, trailer, and dock seal or shelter all meet. Depending on the size of the opening, that gap could result in more lost conditioned air and another $200 to $900 lost annually.

In almost all cases, the first rule of thumb is to look for light along the dock door perimeter—where there's light coming through, there's energy leaving the facility. If there's visible daylight at your loading dock doors (typically on sides and tops of trailers), that means there's a gap to be filled and the right products need to be sourced for each type of gap.

Getting a consistent, gap-free seal along trailer sides, tops, and corners, as well as at the bottom of dock door openings, is essential to creating an environmentally secure and energy-efficient dock. An effective system of sealing products starts with a dock shelter that is specifically designed to overcome the most difficult sealing challenges.

Dock shelter head curtains help seal gaps and create a seal at the top of the trailer. However, sealing and blocking out daylight completely can be a challenge made worse at facilities that are serviced by trailers of varying sizes, where head curtains aren't frequently adjusted correctly to reach lower trailers. Therefore, a head curtain that utilizes weight and gravity to create a solid connection with the trailer top is best, as the weight is necessary to maintain a tight, consistent seal across the full width of the trailer as it bounces during loading and unloading. Also, the head seal must automatically adjust to a wide range of trailer heights without requiring pull ropes or other forms of manual adjustment.

On the sides of the trailer, keep the 2.5 cumulative square feet of opening created by exposed hinge gaps covered completely by hooks on the shelter side curtains. Facility managers should also make sure dock shelters provide a solid seal at trailer top corners, where the side curtains and head curtain come together. This area is notoriously difficult to seal and requires specially designed equipment to ensure an effective seal in this area.

While it is critical to effectively seals gaps at the top and along the sides of the dock opening, don't forget the bottom. Gaps typically exist below and around the leveler and dock bumpers, which present another challenge for energy costs and industrial hygiene. Installing a seal under the leveler can offer a barrier against the elements on the facility's exterior. Inside the dock area, lip corner seals, filler pads, and other components help retain conditioned air inside and warm air from entering.

Inside, HVLS Fans Help Control Heat
While adding air conditioning 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 facilities will benefit immensely from HVLS fans.

Although smaller, floor-mounted fans can be helpful in limited spaces, their high wind speed and noise levels may cause problems. 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 an evaporative cooling sensation of 7-11 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.

A technically advanced HVLS fan can move large volumes of air up to 22,000 square feet and replace as many as 10 to 20 floor fans. By mixing air, HVLS fans also help air-conditioning systems work more efficiently, allowing them to be operated at a set point up to 5 degrees lower.

There are a number of factors to consider when deciding how and where 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 (8-12 foot) fans can be most effective in specific work areas or where installation space is limited.

Fan suppliers can help determine the number, size, and locations that will provide buildings with maximum ROI. They also can help network up to 18 fans into a single control unit and/or a building management system.

Keep Hot Air Out, Circulate Indoor Air
Like most challenges in life, prevention is typically the best solution. A complete seal at the loading dock will help prevent hot air from getting into a facility. On the inside of the facility, HVLS fans are gaining recognition as an efficient way of improving air movement, reducing heat stress, lowering energy costs, and creating a better overall environment.

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 integrity of the products it manufactures, warehouses, or ships. All can have a direct and significant impact on the organization's bottom line.

This article originally appeared in the March 2018 issue of Occupational Health & Safety.