IAQ and The Role of Honeywell Commercial Air Quality Products...

The purpose of this article is to explain how commercial stand-alone air cleaning systems, when properly applied, can accomplish the task of providing improved indoor air quality in commercial businesses. Applications for these types of air cleaning devices include the hospitality industry, which has a high level of environmental tobacco smoke (ETS) and a high level of occupant complaints. The role of stand-alone air cleaners is to lower overall contaminant levels by recirculating the air within the space they serve, filter out both particulate and gaseous contaminants and deliver the cleaned air back into the space. Indoor air quality is improved when contaminant levels are reduced below levels prior to the air cleaner’s use. Improved indoor air quality is achieved when occupants no longer complain and reduced contaminant levels have been proven.

The effectiveness of these devices is strictly dependent upon their mechanical design, the integrity of their components, and the ability of the IAQ professional to apply them properly in varying circumstances. It is important to understand that not all air-cleaning systems are equal in their capabilities. Critical factors such as airflow pattern, particle filtration efficiencies, total weight of gas adsorbing media, and net delivered air volumes vary greatly from system to system and among the many manufacturers. Independent testing conducted by Air Filter Testing Laboratories Inc. (AFTL) and ETL Testing Laboratories (ETL) is an effective way for potential purchasers to be confident that products perform as advertised.

Choosing the IAQ technology that will effectively reduce overall contaminants to the point where occupants are no longer concerned can be a very questionable and confusing endeavor for anyone, especially business owners. Technologies that are touted as the “right solution for you” vary from simple to complex and inexpensive to cost prohibitive. How can those who claim to have the best solutions be sure that a significant level of contaminants will be reduced or controlled enough to satisfy occupant needs? The answer to this question is in the level of expertise an indoor air quality solutions provider has in solving problems and their expertise in properly applying quality products for the purpose of “air cleaning.” It also helps if an IAQ professional understands the proper role of heating, ventilating, and air conditioning (HVAC) systems and how they are a vital part of a well-balanced IAQ solution.

In many instances, side-by-side analysis has shown the installed equipment costs, ongoing maintenance costs, and energy costs can be considerably less for stand-alone commercial air cleaners than other air cleaning technologies. A high-performance, stand-alone commercial air cleaning system can be an economical solution for business owners who do not have the capital to make a large investment in upgrading or replacing their existing HVAC equipment for the purpose of cleaning the air. This alternative method of air cleaning may be the answer for IAQ professionals, contractors and business owners who are looking for ways to reduce project costs while accomplishing the goal of providing improved IAQ.

Before we can understand what poor IAQ is, we must first understand what makes acceptable indoor air quality. It is, at a minimum, a combination of a comfortable temperature - usually 70 to 72 degrees; proper humidity levels - usually 50%; adequate fresh air - enough to dilute CO₂ levels and keep them within 700 PPM of the outdoor ambient; and the absence of excessive and harmful particles (clean air usually contains 250,000 particles or less); and the absence of harmful gases - 0 parts per million or the lowest concentration possible are desired depending on specific gases. Other factors like proper lighting, sounds and vibration waves can also effect the overall well being of occupants and should not be discounted as a contributing cause of poor IAQ. Any variations in temperature and humidity, or excessive levels of CO₂, particles, and gases can cause discomfort to the occupants and the air quality may be deemed unacceptable as a result.

In order to get maximum air cleaning performance from stand-alone commercial air cleaners, they should incorporate the following technology:

High efficiency particulate air filters (HEPA, DOP, & ASHRAE)
Gas phase adsorption/oxidation
High volume of air moved (air changes per hour - ACH)
Coanda air flow pattern and increased ventilation effectiveness
Forward curve blowers with steep fan curves to maintain peak performance
Low initial cost, operation and maintenance

HEPA, DOP and ASHRAE Filters

HEPA and DOP filters are the standard in the industry for controlling contaminants in critical environments like hospital operating rooms, pharmaceutical and semi-conductor manufacturing, food processing, and biological/chemical gas masks. A high performance stand-alone commercial air cleaning system may use this same technology. Other technologies like electronic precipitation, ionization, ozone generators, or outside air are typically not used in these environments because they do not perform as well as HEPA and DOP filters at reducing particulate levels. In addition, certain applications may only require the use of an ASHRAE-rated filter. Because some stand-alone air cleaners use these same critical environment filters, they can effectively provide the highest degree of particulate filtration available, including smoke particle collection. However, air volume must be at a proper level and maintained as close to design as possible.

As an example of a stand-alone commercial air cleaner’s ability to provide a high level of particulate contaminant reduction, independent testing by AFTL has shown atmospheric dust spot efficiencies for this equipment to as high as 99%, and an average of 96.4% efficiency on particles ranging from .3 to 10 microns in size. Additionally, field tests have proven that some stand-alone commercial air cleaners can remove as much as 97% of particles within the spaces they serve.

Gas Phase Adsorption/Oxidation

A sorbent media can be blended to effectively address the gas phase portion of indoor air pollution. For example, there have been reports that some 3500 or more gases can result from tobacco combustion. These gases can irritate the eyes and nasal passages, cause clothes and hair to smell, and discolor furnishings in indoor spaces. Sorbent media collects these gases as air, which contains the gas, flows through the media. Pressure and molecular attraction causes carbon and zeolite to adsorb the gas molecules. Adsorption is the adhesion of a gas molecule to the porous cell structure of the sorbent. Some gas phase filtration changes the chemical make-up of certain gases through a chemisorption process. This reduction of overall gases can improve IAQ.

Removal efficiencies will depend on the adsorbent media bed depth, the velocity of the air and gas mixture moving through the media, and the gas concentration in the air. In order to have high efficiency gas collection, it is critical to have an adequate amount of sorbent media. Systems with low CFM-to-weight-ratios will perform more efficiently than systems on the other end of the spectrum. This relates to resident “dwell” time that a gas comes in contact with the media. A residence time of .01 seconds may give a contact efficiency of 50%, however increasing the dwell time will also increase the collection efficiency.

Contact efficiency for various residence times.

0.005	0.006	0.007	0.008	0.009	0.01	0.02	0.03	0.04	0.05	0.06
29%	34%	38%	43%	46%	50%	75%	88%	94%	97%	98%

In a side-by-side comparison of stand-alone air cleaning systems, not all provided an adequate amount of sorbent media to be effective in the collection of gases. Some manufacturers provide 1000 CFM of delivered air for less than one pound of media while others had as little as 25 CFM of delivered air for every one pound of media. Systems with lower CFM-to-weight-ratios will provide higher collection efficiencies and will also last considerably longer under similar circumstances.

Sorbent Media Performance Chart
Model	Unit Total Net CFM	Sorbent Media Filter Panel Length*	Sorbent Media Filter Panel Width	# of Media Filters Per Air Cleaner	CFM Per Media Filter	Total Square Feet Face Area Per Media Filter	Media Velocity (inches per second)	Media Bed Depth (inches)	Unit High Speed Residence Time (seconds)	Sorbent Media Contact Effic.	Total Weight Per Media Filter Panel (lbs.)	Total Media Weight Per Unit (lbs.)	Total Unit CFM Per Pound
F111C	1000	42.000	11.25	2	500	3.28	30.48	1.75	0.05742	98%	20.00	40.00	25
F118C	425	21.375	12.00	2	213	1.78	23.86	1.31	0.05499	98%	8.00	16.00	27
F113C	300	26.625	10.00	1	300	1.85	32.45	1.00	0.03082	88%	6.30	6.30	48
F113D	300	35.250	10.00	1	300	2.45	24.51	2.25	0.09180	100%	20.00	20.00	15
FM10	1000	40.841	1.00	1	1000	0.28	705.18	0.25	0.00035	2%	0.25	0.25	4000

Note: Field studies have shown that stand-alone commercial air cleaners can reduce gases and volatile organic compounds (VOC) by as much as 90%.

The types of sorbent media commonly used in stand-alone commercial air cleaners are safely and effectively used in many manufacturing processes, military gas masks, and the reduction of gaseous contaminants found in the outside air near chemical and petroleum manufacturing plants and high smog areas.

Air Changes Per Hour

The air volume being moved by any air cleaning system, including an HVAC system or a make-up air unit, is the most critical element of cleaning the air. If air volumes are too low, the system will not be able to keep up with or stay ahead of the generation rate of contaminants. When adequate air volumes are combined with “high efficiency” collection of particulate and gaseous contaminants, significantly lowered levels of pollutants can be achieved, especially when the collection equipment is near the source as in the use of stand-alone air cleaners. When determining the proper amount of air that is required to provide adequate air cleaning for a particular area, one must consider the activity taking place, the volume of the space, and the maximum number of persons that may be present at any given time. If any of these three critical sizing factors are not considered, one may not receive adequate air cleaning capabilities. The result of this mistake would be a dissatisfaction of the air cleaning investment. Unfortunately, this is a common mistake that many IAQ solutions providers make.

Example: One Manufacturer’s minimum recommendations for air cleaning

Application	Minimum CFM Per Person	Minimum Air Changes Per Hour
Banquet Room	30	6
Offices – No Smoking	15	2.5
Cocktail Lounges	35	6

Note: This chart assumes a properly functioning HVAC system with a properly balanced minimum amount of outside air and 4 or more ACH from the HVAC.

Coanda Air Flow Patterns (Multiple Supply/Return Systems vs. Single Supply/Return Systems)

The best example of why airflow patterns are a critical element in air cleaning can be found in the book, “NAFA Guide to Air Filtration,” published by the National Air Filtration Association. Controlled environments like “clean-rooms” are designed to have airflow patterns that minimize the distance that contaminants travel throughout a space and will distribute cleaned air evenly within that space. If the air is not distributed properly or if the quantity of filtered air is inadequate, a product or process may still become contaminated. ASHRAE refers to this as “Ventilation Effectiveness.”

To achieve high collection rates, some air cleaners utilize a Coanda (multiple supply/return) airflow pattern, and when more than one unit is applied the number of supply/return zones increase accordingly. Because of the differential of pressurization created in the occupied space by the air cleaners - supply air is under positive pressure and return air is under negative pressure – contaminants can be quickly moved out of the breathing zone. Proper sizing of the air cleaners will place these positive and negative zones adequately throughout the space they serve to ensure that contaminants travel as little as possible before being captured. Additionally, proper sizing and placement of devices allow Coanda airflow to circulate cleaned air in all areas of the space being treated, minimizing dead areas.

Forward Curved Blowers

To ensure maximum net air volumes from stand-alone air cleaning equipment over the life of media filters, forward curve blowers with steep fan performance curves must be used. As media filters collect and “load” with contaminants, the static pressure associated with the filter increases typically causing a reduction in airflow. It is important for manufacturers to carefully choose fan and motor combinations that can overcome this additional static pressure. This allows the air cleaner to continue to provide the desired air volumes so that design parameters (air changer per hour) are continually met.

Example: Representative Fan Curve Comparison

If fan and motor combinations cannot overcome high static pressures associated with high efficiency filters, air volumes will decrease dramatically. As a result, the air cleaning system can no longer keep up with or stay ahead of the generation rate of contaminants. Usually when this happens, filters are prematurely replaced in an effort to restore the volume of air that the system was originally designed for and maintenance costs rise. High efficiency filters have initial clean filter static pressures ranging from .3” W.G. to 1” W.G. or more, and as they reach their capacity to collect dirt they can add an additional 2 or more inches of static pressure to an air moving system. Because packaged HVAC systems have low static pressure motor/fan combinations, it is very difficult to upgrade them to handle high efficiency filters. As well as a more powerful fan and motor, the filter racks must be changed or modified to handle the larger bag and cartridge particle filters and/or sorbent media type filters.

Independence from the HVAC System

The American Lung Association and commercial air cleaner manufacturers recommend a range from six to ten air changes per hour for most commercial air cleaning applications. Stand-alone commercial air cleaners can easily and economically achieve these circulation rates while providing the highest degree of both gaseous and particulate filtration because they operate independent of the HVAC system and provide constant air cleaning to the space they are treating. Stand-alone systems can address the air-cleaning load independent of the heating or cooling load(s).

For example, a constant volume HVAC system typically cycles on and off as heating or cooling is called for by the thermostat. When temperatures are satisfied the system shuts off, and at this point there is no dilution air coming in from the outside and there isn’t any filtration of contaminants taking place. In a variable air volume system (VAV) the circulation rate is reduced as the temperature becomes satisfied. Because of this, VAV systems must be designed considering the minimum circulation rate required in order to stay ahead of the generation rate of contaminants.

In a one-hour time period, one could estimate that HVAC systems air circulation rates are reduced by as much as 50%. Under this circumstance, the goal of keeping up with or staying ahead of the generation rate of contaminants may be difficult to achieve.

Stand-alone Air Cleaners Could Minimize Outside Air Requirements

By letting the HVAC system do its job of heating and cooling, and letting the air cleaners do their job of air cleaning, outside dilution air can be held to minimal amounts and energy savings may be greatly realized. ASHRAE 62-1999, 6.2 Indoor Air Quality Procedure, allows the reduction of outside air requirements of an HVAC system when adequate particulate and gas phase filtration is used, and explicitly states “Recirculation with air-cleaning systems is also an effective means for controlling contaminants when using the Indoor Air Quality Procedure.” Some stand-alone commercial air cleaners that utilize high efficiency gas and particulate filters can meet or exceed this requirement.

When the outside air does not meet the air quality standards in Table 1 of ASHRAE Standard 62-1999, then the IAQ procedure must be followed. Areas of outside air concern include major cities, industrial complexes, manufacturing complexes, high vehicle traffic areas, and airports. Concern should also be taken in areas where mold and pollen counts soar periodically. Outside air is very important in order to maintain comfortable and healthy indoor air quality and it is not recommend to have less than 5 CFM per person of outside air for any occupied indoor environment. ASHRAE recommends an outside air amount that will maintain CO₂ levels indoors to within 700 parts per million of the outdoor ambient. Finding the minimum amount of outside air required to meet this standard may fall below the amounts in the standard’s Table 2, which would therefore provide energy savings.

For example, when outside air is introduced, it generally has to be heated or cooled and the humidity has to be controlled, at a minimum. This can cost anywhere from $1.50 to $3.00 per CFM annually in energy consumption. If an additional 2000 CFM of outside air is being considered for air cleaning (dilution), annual energy costs can increase by as much as $3,000 to $6,000 and a cooling capacity from 5 to 10 additional tons may be required depending on the CFM per ton equation applied. In this scenario, the additional installed-price for tonnage that is required, only for the purpose of air cleaning, could be as much as $2500 per ton.

Using high performance commercial air cleaners instead of outside air for the purpose of air cleaning, HVAC and energy consumption costs are reduced and enough money could be saved to pay for air cleaning equipment and ongoing filter maintenance. In most cases, the energy savings alone is enough to pay for commercial air cleaners and their maintenance in a very short period of time.

In addition to the economic advantages of using stand-alone air cleaners, in lieu of outside air, for air cleaning purposes, it should be noted that a study published in the New England Journal of Medicine, March 1993, titled “The Effect of Varying Levels of Outdoor-air Supply on the Symptoms of Sick Building Syndrome,” showed that increasing outside air does not always alleviate sick building syndrome.

Low Initial Cost, Operation and Maintenance

Operating stand-alone commercial air cleaners and providing proper maintenance and filter changes is less expensive than exhausting contaminants and bringing in large amounts of outside air for dilution 1. Up-front HVAC equipment costs are reduced, the life expectancy of the system is extended and maintenance and repairs are reduced because the HVAC system doesn’t have to work as hard as it would with the additional load and constant operation prescribed by ASHRAE’s Ventilation Rate Procedure. This extra hard work would be the result of the fact that typical HVAC systems are designed for thermal comfort and not high level air cleaning.

Conclusion

There are economical approaches to providing acceptable indoor air quality that can provide a high rate of return on your investment. When a business owner, HVAC or IAQ professional considers the alternatives for air cleaning, it is important for them to compare the initial equipment purchase price, installation labor and material costs, on-going energy consumption costs, on-going maintenance costs, and most importantly, results based performance. The system that provides the lowest overall cost will provide the quickest return on investment, and the system that provides the greatest contaminant reductions will contribute the most to acceptable IAQ.

Furthermore, by providing acceptable indoor air quality in occupied spaces, business owners may realize a significant increase in employee productivity and attitude and possibly an increase in revenue where paying customers are IAQ concerned. Taking a proactive approach to providing good indoor air quality can also reduce the number of complaints from employees and customers, which could mean increased revenue and profits for most businesses, and possibly prevent liability issues in the future.