Three steps to meet your indoor air quality goals
Maintaining healthy air quality is essential to operating a successful plant. This article introduces a three-step process that can help you reach your IAQ goals.
By Eileen Duignan-Woods, P.E.
Whether you’re planning a new plant or are responsible for operating an existing one, it’s critical to have a strategy to ensure high HVAC performance and a healthy IAQ. A three-step process can help — identify the problem; gather the data and analyze, analyze, analyze; then arrive at a solution (using consultants, if necessary).
Start with an up-to-date plan view of the facility. Document the HVAC criteria each area requires, from the dock that receives raw material to the dock that ships finished products out the door. List each area on a spreadsheet and document its problems by asking a series of questions that will keep you from jumping to an incorrect conclusion or solution.
- Does the cleanliness of the air in the space (ordinary dirt as well as odors) indicate a contamination problem?
- Have the applicable ventilation codes changed lately? If so, identify and document.
- Has new production equipment, using new quantities of exhaust air, been installed in recent years?
- Is the HVAC in the office and other critical areas “positive” (more air supplied than exhausted) relative to the rest of the plant?
Check the governing ventilation codes and how they affect each part of the plant. Bear in mind that although the HVAC requirements for products and workers might be different, they must still coexist. One or the other will dominate the major portion of the plant. Some areas will become more critical than others as you seek quality of product, a clean, healthy facility and a performance-optimized HVAC system.
Color-code different building plan areas using pencils or CADD (the best way) and overlay a sketch of the HVAC systems. Identify clearly the requirements for each space as well as what actually exists. Keep a hard copy of this overall plan handy as you analyze each area. If necessary, seek help from technical societies or industry standards as to what constitutes good environmental criteria for your plant.
Understanding the relationship among different areas of your plant and the relative cleanliness and ventilation rates each requires might be a challenging task, but it’s essential to good performance and IAQ.
Check the ductwork and air distribution to determine if any HVAC systems are feeding conditioned air to multiple plant areas having different criteria. Look for overlap in areas being served. Don’t heat or cool large, vacant spaces where there is neither product nor workers. See if production can be isolated from areas that tend to contaminate air.
A plant cluttered with miscellaneous HVAC equipment probably started out with good centralized, customized air handlers designed to treat and distribute air for a certain production scheme. Through the years, as production changed, auxiliary heating and cooling became necessary. Budget-sensitive commercial equipment was probably added for certain small spaces. Collectively, this mass of equipment not only fails to do the industrial job, but eats into the plant’s energy efficiency and multiplies its maintenance requirements. Extraneous equipment represents another vehicle for dirt, moisture and pollution to enter the plant. In an effort to save energy, complicated controls might have been added. Bad decisions about air distribution could have exacerbated the energy problem.
Examine and document the physical condition of the HVAC equipment. Start a permanent log that lists the technical data and physical condition of each piece of equipment, including age and the area it serves. Look for equipment and systems serving areas in which performance requirements have changed. Ask if the equipment can do its job in a reliable and efficient manner or whether it should be replaced.
Review the humidity situation. Too much or too little can wreak havoc with your product, increase HVAC energy demand and never provide a comfortable environment. The same building, placed in a different part of the country, will present entirely different considerations. Dry winter environments typically plague the North. Excessive humidity during summer months is the enemy of production in the South. Likewise, your production process might be producing an excessively humid or dry environment anywhere in the plant.
Solutions will appear
Consider eliminating overlapping ductwork and replacing ductwork with industrial air diffusers or nozzles that throw large quantities of air long distances. If ductwork interferes with maintenance, another consideration might be fabric ductwork. When work is necessary, simply deflate the ductwork and pull the fabric aside like a shower curtain. The installation cost might be less than half the cost of using standard ductwork. The fabric is durable and easy to maintain. Both solutions reduce static pressure loss, save energy and help maintain HVAC exactly where you need it to be.
Test and balance the air systems. Most HVAC systems are badly out of balance within five years of installation. Hire a certified test and balance contractor to put your system in order after you finish your hardware and ductwork changes. You might be pleased to discover a lot of that auxiliary heating and cooling equipment can now be abandoned or used elsewhere as a result of good testing and balancing.
Bring the systems up to code and look for opportunities to reduce outside air. Erecting barriers around production areas might reduce required illumination, outside air ventilation and contamination immediately while improving control of critical temperature and humidity. Having smaller functional areas reduces the need for HVAC treatment.
Stratification of the HVAC system works well in many plants. It involves bringing the air diffusers down to a level where treated air is needed. This allows adjustable-head industrial diffusers to produce a quality environment while avoiding air-conditioning the ceiling.