ROSS Air Emissions Regulations and Your Emergency Generator

Under the ROSS program, emergency generators and other low-emission sources can be registered with the IEPA instead of requiring a full permit.

What is the Registration of Smaller Sources (ROSS) Program?

The ROSS program is intended to simplify air-permitting requirements by requiring sources with low emissions, such as emergency generators, to register with the Illinois Environmental Protection Agency (IEPA) rather than obtain a permit. As an added benefit, ROSS sources are not required to submit an annual emission report.

ROSS was established to meet State of Illinois air emission regulations. The regulations require owners of reciprocating internal combustion engines to register with the state. For the vast majority of emergency generators, the regulations require only an initial registration, annual record keeping, and an annual fee.

According to the Illinois EPA, there are 6,457 air emission sources now permitted across the state. ROSS would apply to an estimated 3,250 of those sources. The ROSS program results in a substantial cost savings for those sources, with a $235 annual registration fee instead of the current air permit fees of up to $3,400 for this group. The Illinois EPA states that ROSS results in little or no impact on air quality because the larger sources — that would still need a standard permit — contribute more than 99 percent of the total air pollution, while eligible smaller sources emit less than 1 percent. ROSS will also allow Illinois EPA to focus on major sources of air emissions.

Environmental Consulting Group has helped several downtown Chicago buildings obtain the ROSS registration. In many cases, the building was unaware of this requirement until their non-compliance was noted in an internal audit.

How does one determine whether my source is eligible?

It should be noted that most emergency generators in high-rise buildings easily meet the ROSS eligibility requirements.

To determine ROSS eligibility, one must calculate the actual emissions of the emergency generator using AP-42 emission factors. When Environmental Consulting Group helps their chief engineer clients with the initial registration, they obtain the actual emissions of all the criteria pollutants associated with their generator. The criteria pollutants include nitrogen oxides, carbon monoxide, sulfur oxides, particulate matter, volatile organic compounds, and other air pollutants.

To qualify for ROSS, one must confirm that the total actual emissions are less than the following limits for the prior calendar year:

5.0 tons/yr. of combined pollutants (particulate matter, carbon monoxide, nitrogen oxides, sulfur dioxide and volatile organic material)

0.50 tons/yr. of combined Hazardous Air Pollutants

0.05 tons/yr. of mercury emissions

0.05 tons/yr. of lead emissions

ECG then adds them to any other possible emissions on the site to determine if the facility exceeds the combined pollutant thresholds for ROSS eligibility. As stated above, most, if not all, downtown office buildings would easily meet this criterion.

The entire ROSS regulation can be found at 35 Ill. Adm. Code 201.175.

Case Study

Class A Commercial Office Building

North Franklin Street

Chicago, Illinois

In August 2016, ECG was contacted by a chief engineer of a building located in downtown Chicago that wanted to apply for a ROSS permit.

Emergency Generator

The first step in the process involved ECG providing the chief engineer with a questionnaire. Along with basic information about the site, the form listed the following questions to determine ROSS program eligibility:

Do you have a financial arrangement with a power supplier (e.g. do you sell generated power back to the utility)? Yes ☐ No ☐

Do you operate your emergency generator for more than 100 hours per year?

Yes ☐ No ☐

Please list all of the active reciprocating internal combustion engines that you have on site, including the respective horsepower rating, fuel type, and year of installation:

Engine #1



Fuel Type: 

Year of Installation: 

Annual Hours of Operation: 

Annual Fuel Usage (gal.):  

Using the above information, ECG then calculated the air emissions from the generator.

For this generator, ECG calculated the actual combined air emissions at 0.0301 tons per year. ECG also calculated the actual combined Hazardous Air Pollutant emissions at 0.0005 tons per year.

Since the criteria is less than 5.0 tons per year of actual combined pollutants and less than 0.50 tons per year actual combined Hazardous Air Pollutants, the emergency generator at this building easily met the criteria for a ROSS permit

The next step involved filling out the two-page ROSS application with the chief engineer. After the application was completed and signed, ECG sent the form to the Illinois Environmental Protection Agency with a $235 check.

Approximately two weeks later, the client received a letter from the IEPA stating:

“The Illinois EPA hereby acknowledges receipt of your registration and confirms that your source has been registered in the Registration of Smaller Sources (ROSS) Program. The ROSS Program regulations can be found at 35 Ill. Adm. Code 201.175. Although the source is not required to have an air permit during the period it is registered as a ROSS eligible source, please be advised that the source must still comply with all applicable laws and regulations.

For further information on the ROSS Program please visit the website at”

After the initial registration, what are the ongoing requirements and costs?

As stated above, aside from minor record keeping requirements, payment of the $235 annual fee will serve as the owner’s or operator’s verification that the source continues to meet the eligibility criteria and will automatically renew the registration under ROSS.

Chief engineers wanting to learn more about how ECG can help with the ROSS registration process can contact Environmental Consulting Group at (630) 607-0060.

Posted by on Feb 1st, 2018 and filed under News. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.

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