Manufacturing comfort

Indoor air quality: Air movement needed in supply chain facilities
By Nina Wolgelenter, Big Ass Fans May 20, 2013

Figure 1: Temperature and air quality are two important factors that require attention when considering plant productivity. Courtesy: Big Ass FansThat comforting feeling created by an outdoor breeze on a hot summer day is equally satisfying to workers within a warehouse setting where fluctuating temperatures and stagnant air are the norm. Considering your equipment is only as good as the people using it, creating a comfortable work environment with the simple addition of air movement improves the health, safety, and sanity of those within.

Supply chain facilities are prone to these fluctuating temperatures; it’s an unfortunate reality of warehouse design. Air-conditioning and ventilation systems, while effective up to a certain point, can be greatly enhanced by the addition of proper air movement. When interior conditions are such that workers can no longer concentrate on the job at hand, personal comfort must be addressed. 

Comfort

In terms of employee comfort, it’s important to understand that the sensation of feeling comfortable is not dependent on air temperature alone. Human thermal comfort takes into account numerous environmental factors including temperature, thermal radiation, humidity, and air speed as defined by ASHRAE Standard 55-2010, along with personal factors including activity level and clothing type. Studies have shown that improved occupant comfort leads to increased productivity, with worker productivity decreasing as temperatures rise above 77 F. 

The spin

In warmer months, operating between 60% and 100% of maximum speed, 6- to 24-ft-diameter fans improve comfort with either an evaporative cooling effect or the added effect of heat transfer—when skin temperature is warmer than air temperature. Although fans do not lower the air temperature in a space, the perceived cooling effect can make a person feel up to 10 degrees cooler.

In the winter months, operating at 10% to 30% of the maximum speed, large-diameter, low-speed fans successfully destratify tall spaces, mixing the warm air at the ceiling level with the cooler air at the occupant level, creating a more uniform temperature.

The addition of air movement offers multiple benefits that improve the well-being of occupants and, in some cases, of products and machinery as well, by aiding in the following:

  • Reducing heat stress on employees
  • Reducing condensation to preserve product integrity
  • Improving indoor environmental quality (IEQ), when mold or toxic fumes are airborne
  • Providing year-round comfort 

Heat stress

OSHA standards indicate temperatures of 100.4 F and above are dangerous for workers while air temperatures that exceed 95 F significantly increase the heat load on the body. When temperature and humidity rise, the body’s ability to cool itself decreases, severely affecting worker productivity. 

In the manufacturing industry, reducing activity level is generally not an option, but applying gentle, nondisruptive airflow from large-diameter, low-speed fans bring about the evaporative cooling process.

A Texas-size problem

A Texas-based McGraw-Hill textbook distribution center faced up to 15 heat-related incidents each summer in its 900,000-sq-ft facility. The 200 workers who boxed and shipped textbooks needed to ramp up productivity during this time in preparation for the fall semester, but the extreme Texas heat made this a tricky proposition.

Thirty 24-ft diameter fans were installed to help circulate the air. “It was an oven in this concrete building, and when workers were hot, they slowed down,” said Mike Price, maintenance manager. “We’ve noticed a big difference (installing the fans). One hundred and five is still hot, but it’s manageable inside with the fans.” 

Blowing condensation to bits

Figure 2: Condensation is another that HVLS fans can help solve. Condensation is an issue of safety, especially on concrete floors. Courtesy: Big Ass FansCondensation within a warehouse space can prove detrimental to employee safety (e.g., forklifts on wet concrete) and negatively affect product integrity. Dehumidification systems (air conditioning) can decrease moisture content of the air, while heating systems help increase air or surface temperatures to help reduce moisture buildup.

The downside however, is that large industrial spaces are often impractical, or at the very least expensive to heat and cool. Air movement, on the other hand, does not depend on any external conditions to be effective.

Properly designed large-diameter fans with airfoils and winglets disturb the thin film of stagnant air on the metal surface, which in turn dramatically reduces the likelihood of condensation. This is highly beneficial in areas of high humidity where moisture buildup can result in mold and mildew.

Where condensation is a concern, the temperature of a concrete slab will trail the air temperature by about a month. For example, as April’s air warms to 70 F, the concrete is still stuck at roughly 50 F, from the month before. This warm, moist air sits on the cold slab and deposits moisture as it cools.

Given the vastness of most facilities, the steady, even air movement from large-diameter, low-speed fans helps move the stagnant warm air off the cold surface before it has a chance to cool down enough to leave puddles. Fans with additional blade-ending fins can help direct the fan’s airflow toward the floor, maximizing the fan’s coverage area. 

A slippery mess

John Rock Inc. of Coatesville, Pa., goes through 250,000 ft of green hardwood and 9,000 lbs of nails to create 20,000 pallets every shift. Greenwood hardwood is between 30% to 45% moisture, which was causing condensation within the facility.

“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,” said Penn Cooper, business development and purchasing manager. “Here, we spent a lot of money to make sure we had a very smooth floor so we could move efficiently. We created a huge skating rink issue, just because it was wet. People were getting hurt.”

On top of the slip-and-fall risk, the moisture also allowed mold to flourish on the newly constructed wooden pallets. Both issues were addressed by the addition of air movement from six 24-ft diameter, low-speed fans used to thoroughly mix the air.

The result is only a slight temperature difference from floor to ceiling and reduced opportunity for condensation to form. Rather than using dozens of small fans to blow directly on the ends of the pallet rows, the 24-ft diameter overhead fans efficiently and effectively circulate air throughout the space. 

Product integrity case in point

Kentucky-based Owensboro Brick & Tile manufactures 35 million bricks annually, running its kilns at 1,950 F. The staging area holds 300,000 to 400,000 bricks at a time as they dry before going into the kiln. “We have to get a certain percentage of moisture out of the brick before we can fire it,” said Mark Sexton, plant manager. As one set of bricks would come out the kiln, the steam would keep the area hot and perpetually wet, preventing a thorough drying. The four 16-ft diameter, low-speed fans were installed to increase the air speed in the drying area, helping to evaporate the moisture from the green bricks waiting to be fired, while also dissipating heat and moisture from the steaming bricks exiting the kiln.

“These fans are helping to remove the moisture from the brick,” Sexton said. “So it’s actually letting me run our kilns a little faster to get more product out, because the bricks are drier.” 

Improving IEQ

Figure 3: The use of HVLS fans in supply chain facilities can improve worker comfort. Courtesy: Big Ass FansAll buildings, regardless of age, are susceptible to deficiencies in indoor environmental quality (IEQ). New and renovated construction are prey to tighter building envelopes that can reduce ventilation system effectiveness, and humidity and moisture buildup can cause unforeseen effects for building occupants in regard to bacteria and mold growth.

Large-diameter, low-speed fans play a significant role in improving IEQ by turning the air in the space over several times per hour, ensuring good air distribution. This increased air circulation allows for more constant, uniform temperatures that help inhibit mold growth. 

Moldy proposition

WestWind Logistics in Omaha, Neb., washes and then stacks up to 50,000 wooden pallets to dry before putting them back into service. Any pallet that sprouts mold must be rewashed, costing time and money. Unfortunately, the warm, humid warehouse was the perfect environment for mold, and wood is among mold’s favorite places to set up shop.

“If the pallets sit here too long, they mold. At one point, we had 4,000 pallets in the warehouse, and over half of them got moldy,” said Vincent Hoy, facility manager. “We have to rewash anything that has mold on it or touching it, so that’s two days of work lost.”

The air movement from the two 20-ft-diameter, low-speed fans that were installed disturb the thin sheet of stagnant air surrounding each pallet, helping to prevent the establishment of mold by speeding up the drying process on surfaces on which mold can form. “About 95% of the stock we put under the fans never molds,” Hoy said. “We put everything we wash and sort under the fans—that’s the premium real estate.”

Whereas most warehouse-style facilities don’t have air conditioning, they do employ heating systems in the winter months. On the human front, adequate IEQ is typically a concern between 3 and 72 in. from the floor, which is considered the occupant breathing zone. When using a traditional HVAC system in the winter, only about 80% of the fresh air brought into a space reaches the designated occupant level, which means the system must compensate for the lost air to create a space that complies with ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality.

The addition of large-diameter, low-speed fans to circulate the air down to the occupant level not only helps to keep IEQ levels in check but reduces reliance on the HVAC system altogether. This air circulation also compensates for the insufficient mixing of the supply air and room air, and the natural buoyancy of the hotter air allows it to remain at the ceiling level. 

Airing on the side of safety and comfort

Fortunately, there is a middle ground between surrendering to the expense of air conditioning and suffering a continual loss of profits due to comfort-related problems. According to the Center for the Built Environment, temperature and air quality are two of the most important factors when considering productivity.

At the forefront, using large-diameter, low-speed fans is cost effective both in terms of worker productivity and reduced operating costs. Ideally, worker comfort leads to safer working conditions as employees can spend more energy on the task at hand without experiencing heat discomfort or exhaustion. This in turn results in increased worker productivity, positively affecting the bottom line, considering fewer days are missed due to illness and accidents.

Following that same agenda, businesses are able to keep workers comfortable in a far more energy-efficient manner, reducing operating costs and dependence on expensive heating and cooling systems.