(Air) Moving Experience
The simple addition of air movement improves safety, comfort, and productivity.
- By Nina Wolgelenter
- Jul 01, 2013
When lakes spring up in the middle of warehouses, facility and safety managers can either reach for their fishing pole or take a good look at worker safety conditions.
Condensation buildup, chemical exposure, poor indoor air quality (IAQ) -- these are just a few of the concerns that plague warehouse facilities. While there is no panacea, the introduction of effective air movement by way of high-volume, low-speed (HVLS) fans up to 24 feet in diameter works with existing conditioning systems or on their own to create a healthier, safer, more comfortable environment. By improving these variables, increased productivity prevails.
Big Fan Fundamentals
Understanding how HVLS fans circulate and distribute air is the first step in realizing the vast potential air movement can provide, especially when it comes to safety.
Properly engineered HVLS fans take advantage of their size, not speed, to move massive amounts of air. When the airfoil length is doubled, you’ve increased the surface area that those airfoils sweep times four. As the size gets larger, the amount of air the fan moves increases at a much faster rate than the amount of power it takes to turn it. So, with all things being equal, a larger fan, up to 24 feet in diameter, becomes more efficient. Additionally, AirFences installed along the airfoil redirect air that would otherwise slide off and be lost. This technology increases efficiency while contributing to a 28 percent improvement in coverage area.
By design, airfoils -- blades -- play a large role in determining the effectiveness of a fan. The shape of the foil combined with its pitch, or angle of attack, are key parameters in determining amount of air moved with the energy required in the effort. An exaggerated pitch -- airfoils with an almost vertical angle of attack -- will increase drag (and increase energy draw), while a flat, mostly horizontal airfoil will typically not move much air at all; the most efficient angle lies somewhere in between.
Design engineers use the term thermal comfort when designing a space where occupant comfort is a factor. It's important to understand that while air temperature is a strong contributing factor to comfort, it's only one of several important variables. Human thermal comfort takes into account numerous environmental factors, including temperature, thermal radiation, humidity, and air speed as defined by ASHRAE Standard 55-2010 (American Society of Heating, Refrigerating, and Air-conditioning Engineers), along with personal factors that include activity level and amount of clothing.
Whereas the safety benefits of air movement might not seem apparent at first, take into account the following scenarios and the drastic improvements realized through the installation of HLVS fans, regardless of the season.
Condensation occurs when warm, moist air contacts a cold surface. As the air cools, it loses its ability to store moisture. In the summer, for example, condensation is displayed as water droplets on cold beverage cans. But in the spring and fall, temperature swings and the accumulation of condensation can wreak havoc in a variety of workplaces. Air movement from HVLS fans thoroughly and gently mixes the air and equalizes temperatures, reducing the opportunity for condensation.
John Rock Inc. of Coatesville, Pa., goes through a quarter-million feet of moisture-rich green hardwood and 9,000 pounds of nails to create 18,000 to 20,000 pallets each shift. "Green hardwood is between 30 and 45 percent moisture content," said Penn Cooper, business development and purchasing manager. "Forklift traffic and employees walking, with that kind of moisture, was a huge issue, particularly as the weather changes though the spring or the fall."
Dew point-related issues occur when the surface of the concrete slab is at or below the saturation point of the air. In the spring, a concrete slab will trail the air temperature by about a month. So while the April air is at 72 F, the slab might still be stuck in March at 50 F. Warm air sits on this cold slab, dropping moisture as it cools. In the fall, cold materials coming off a truck into a warmed space can cause the same effect.
"At our old facility, the floor was so rough and beat up, it didn't matter if it was wet, there was still lots of traction," Cooper said. "Here, we spent a lot of money to make sure we had a very smooth floor so we could move efficiently. Well, we created a huge skating rink issue, just because it’s wet." The result was a huge safety risk due to the moisture accumulation.
Six 24-foot-diameter HVLS fans were installed to mix the warm air from the rafters with the cooler air at the occupant level, resulting in just a slight temperature difference within the space, essentially eliminating the condensation issues. Without condensation, product integrity is restored without the fear of moisture damage.
At the same time, this same air flow works to combat localized humidity issues and the resulting mold growth that can exist.
As stated above, the air movement provided by the fans prevents the buildup of moisture on surfaces by continually disturbing the thin sheet of stagnant air on equipment and goods, significantly improving IAQ concerns. "Increasing air movement near this surface replaces moisture-laden air with drier air, increasing the rate of evaporation and promoting drying," said Jason Hollan, manager of systems engineering at Big Ass Fans.
According to the Center for the Built Environment, temperature and air quality are two of the most important factors when considering productivity1, and the introduction of HVLS fans addresses comfort and safety issues while maintaining a fundamentally sustainable operation.
While businesses like John Rock, Inc. must contend with mold, chemical vapors in the air prove to be an equally invasive IAQ issue. Employees at the Environmental Service Center Household Hazardous Waste drop-off facility in Houston endured the double whammy of exhaust fumes from the cars driving into the warehouse and chemicals and pesticides city residents were permitted to dispose.
With 13,000 square feet, this facility's layout of wide-open north/south bay doors and a 27-foot ceiling did little to improve conditions. "Even with the bay doors open, we didn't have much air circulation," said Roger Jones, the facility manager. "Many days, there was no air movement at all." Jones said they had tried various other fans in the facility but nothing was able to offer the level of cooling his staff needed. Equally important to Jones was the fan's ability to diminish the vapors present in the air. Household hazardous waste accepted at the site, including antifreeze, fuel, oil, paint, pesticides, and cleaning products. As these mixed with the stagnant air and vehicle exhaust fumes, the air was "a hazard in itself," Jones said. "We deal with not only the ambient temperature, but the odors from all those chemicals we handle, and the fans help move those odors out of our breathing zone." The gentle breeze allowed employees to move about more comfortably while also helping to disperse unhealthy vapors permeating the air.
Air movement not only improves IAQ, but it also boosts morale, leading to an increase in productivity. When temperatures impede employee performance, air movement from HVLS fans improves it. The increased air speed doesn’t actually lower the air temperature, but rather, works in concert with the body’s natural cooling process to produces a cooling effect of up to 10 degrees F.
OSHA standards indicate temperatures of 100.4 F and higher are dangerous for workers, while air temperatures that exceed 95 F significantly increase the heat load on the body.2 When temperature and humidity levels rise, the body’s ability to cool itself decreases. Productivity is directly related to profit, which is, in turn, related to comfort. Increase the comfort and you’ll increase productivity and therefore increase profits at the same time.
Studies indicate there is an average 2 percent reduction in work performance per 1.8 F temperature rise when the temperature is above 77 F. While this may not seem detrimental on an individual basis, this drop in employee productivity can add up to huge profit loss across a company.
In addition to safety benefits that accompany summer cooling, winter heat destratification has equally favorable results. At New Hampton Metal Fab, whose facility has little to no insulation, employees were at the mercy of the weather outside. "All of the heat was going up," a manager explained. "We'd send somebody up to fix something and they would strip down to their long johns, while the guys on the floor were standing there in Carhartts, basically freezing."
An 18-foot-diameter HLVS fan was installed to mix the warm and cool air, which created uniform temperatures and improved indoor comfort. It also improved the dexterity of the employees because they were able to shed their extra layers.
Heat stress is defined as a group of conditions that result from being overly exposed to or overexertion in excessive ambient temperatures. Adding HVAC to a facility may not always be feasible or efficient, but incorporating air movement from HVLS fans can create a cooling effect for employees working in non-conditioned spaces. Employees at the Century Metals & Supplies, Inc. 60,000 square foot facility in Miami Gardens, Fla., were subjected to unbearable working conditions during hot summer months. Stationary floor fans sporadically placed throughout the facility proved inefficient in delivering any comfort.
"Our employees continuously complained about the heat and the excessive amount of sweating that occurred while working," explained Julie De Leon, human resource officer at Century Metals. "We have two windows in the warehouse, but they aren't big enough to bring in a noticeable amount of air."
Three 24-foot-diameter HVLS fans were installed to evenly distribute air throughout the facility, offering a cooling effect as well as increased safety as the floor fans have since been removed. The difference was immediate, Leon noted. "Our big fans work great, it's truly amazing the strength they have and the amount of air they move. You can really feel it when you walk into the area because the air just spreads all over and we no longer have complaints from our employees," she added.
Sum of All Parts
Property designed HVLS fans allow facilities to eliminate the use of ineffective floor fans, freeing up floor space and avoiding the safety hazards that come with excess cords lying about; the quiet operation actually allows employees to hear fish jump.
Warehousing facilities, whether used for distribution or manufacturing, are notorious for fluctuating temperatures, and equipment is only as good as the people who operate it. When conditions within a facility are no longer favorable, worker productivity inevitably takes a nose dive, bringing profits down as well. Introducing proper air movement is a definitive factor in the success of many businesses, providing the necessary comfort while improving safety.
1. Center for the Built Environment. "TechNotes: Productivity and IEQ Satisfaction."
2. Occupational Health and Safety Administration Technical Manual, Section III: Ch. 4; Heat Stress. 1999