The ASHRAE 62 Standard has two methods for determining the necessary outdoor air levels: the Ventilation Rate Procedure and the IAQ Procedure.

The Ventilation Rate Procedure is the easier of the two to apply and the vast majority of buildings are designed and operated under its guidelines.  The ventilation standard specifies a certain number of cfm per person for various types of buildings.  For example, in office spaces and schools, the HVAC system must bring in 13 to 16 cfm/person of outdoor air, depending on occupant density.When the ventilation rates were adopted in 1989, two things were assumed: 1) the only means of dealing with contaminants in the space is by dilution with outdoor air (i.e. there is no air cleaning); and 2) the outdoor air level is sufficient to accommodate "moderate smoking" (based on 30% of the occupants smoking 1 cigarette per hour).  Later, standards were amended to allow 15 cfm/person in non-smoking offices.  Today, the ventilation standard also requires that the outdoor air quality meet certain criteria.  In practice, however, this is something that is not often determined or monitored.

The IAQ Procedure allows for greater fine-tuning and more efficient operation of the HVAC system and the outdoor air levels.  However, because it utilizes a series of complex calculations, it is less straightforward to use than the Ventilation Rate Procedure.  The IAQ Procedure gives designers and operators, in essence, outdoor air credit for things such as no smoking, good airflow patterns, and air cleaning.  ASHRAE has developed formulas for calculating contaminant levels in a space and guidelines as to what levels are of concern.  The Dynamic AirQ™ Program puts these in a format that is easy to interpret, and makes meaningful predictions for CO₂ and contaminant levels.

The Dynamic AirQ™ Program also uses location specific climate and energy data to calculate potential operational savings. The ability of Dynamic Air Cleaners to control particles, biologicals, and VOC's ensures superior air quality and generally allows for significant reductions in outdoor air requirements. 

Operational Savings

In a typical building with no smoking and no unusual contaminant sources, outdoor air levels can often be reduced to between 7.5 and 10 cfm/person.  Such a reduction can yield significant operational savings.  For example, in a small office building with a 60-ton rooftop unit, annual savings on utility costs can be expected in the range of $3,000 to $12,000 depending on the geographic location of the building (hot humid climates have the greatest costs/savings), the utility rates, and the hours of operation.

Capital Investment Savings

Reduced outside air can also favorably impact equipment selection, sometimes translating into smaller tonnage equipment. This has had the net effect of paying for the air cleaners on many jobs.  In one recent project involving the renovation of a 22-story Federal Court House in Philadelphia, the use of Dynamic V8 Air Cleaning Systems reduced outside air requirements enough to preclude the necessity of installing return air fans in the 23-year old building in order to comply with current Ventilation Rate Procedure levels.

Improved IAQ

The other benefit to this approach is that outdoor air is the most common source of IAQ problems in a building, e.g. the entrainment of vehicle and kitchen exhaust, ultra-fine particles and odors into the air intakes.  With the banning of smoking and modern sustainable building materials, outdoor air is typically more polluted than indoor air in any urban environment.  For example, at the ASHRAE Headquarters in Atlanta, constant monitoring of indoor air and outdoor air over the last three years showed that indoor air is usually substantially cleaner than outdoor air. And in the monitoring of black carbon and ultrafine levels inside and outside an office building in Washington, DC, the indoor levels were 92-99% lower than those outdoors.  While it is true that both buildings have Dynamic V8 Air Cleaning Systems, the larger point remains that bringing dirty outdoor air indoors does not improve IAQ, whereas cleaning and re-using the indoor air does.