Why Do I Need Air Permit?

This is a frequent question Caltha receives, often because determining if your whole facility, a single piece of equipment, or your process change requires an air emission permit requires a technical evaluation and relies on calculations which, to many, defy logic at first.

There are two primary reasons a facility or process requires an air permit:

1. It falls into a listed category of manufacturing processes which always requires a permit, usually referred to as NSPS or NESHAP standards; or
2. Potential air emissions exceed specific thresholds.

In most cases, facilities subject to NSPS or NESHAP standards are well acquainted with air permitting requirements; therefore this summary focuses on #2.

How Do I Determine If I Will Exceed Permit Thresholds?

The permit thresholds for regulated air pollutants are listed in federal and State regulations. Facilities must determine their Potential To Emit, or PTE, in order to determine if they exceed these thresholds.

How Do I Determine My Potential To Emit?

Determining the PTE for a facility or process requires a technical evaluation of the process, including maximum throughput, process chemistry, and production bottlenecks, to estimate the maximum hourly emission rates for all regulated air pollutants. This maximum hourly rate does not include the removal efficiency of any pollution control equipment (such as baghouses, thermal oxidizer) being used.

Once the maximum hourly rate is determined, it is multiplied by 8,760 to estimate the maximum annual potential emissions. This value assumes the maximum emission rates are achieved 24 hours per day, 7 days per week for a full year.

But I Don’t Operate 24/7…

Few facilities actually operate for 8,760 hours per year. However, the Potential To Emit calculation uses this value only to compare to the permit thresholds. Your actual emissions will likely be much lower.

Why Can’t I Take Credit For Pollution Control Equipment?

If a facility needs an air emission control permit, many of the permit requirements will involve how the pollution control equipment is operated and maintained to ensure effective control. The benefits of the pollution control equipment will be measured in actual emission estimates.