Environmental Compliance for Emergency Power Generators

Emissions Reduction & Compliance
PEN #21


On August 14, 2003 fifty million people in Ontario and the U.S. were subjected to a real time test of their emergency preparedness. Subways and traffic came to a halt, cell phone service, escalators and elevators stopped and fuel for vehicles and emergency power generators was difficult to come by.

Not surprisingly, the power failure was a wake-up call for emergency preparedness and property managers are taking steps to keep their buildings operational and tenants secure by installing emergency power generators. However, before you install and operate an emergency generator you are required by law to obtain an operating permit from the Ministry of the Environment. The permit is called a Section 9 Certificate of Approval air permit and advance planning is absolutely necessary since the MOE’s application review process can take months even if there are no non-compliance issues.

The MOE recognizes that emergency power generation is necessary; consequently, they have developed a streamlined permit review process that primarily focuses on the nitrogen oxides (NOx) and noise emissions from the equipment and the impact of these contaminants on the nearest sensitive receptor such as a hospital, day care centre, school, place of worship, residence, or apartment building. The time and cost to conduct a preliminary assessment to ensure that the proposed equipment can comply with the respective air and noise limits is minimal compared to the cost of having to retrofit equipment, or worse, having to replace or relocate equipment that cannot comply.

The purpose of this information bulletin is to make building owners, property managers, and operators aware of the environmental issues that should be considered before you purchase and install an emergency generator. Consideration of these few points could save you time and money, and hopefully expedite the permitting process.


In Ontario, a MOE Certificate of Approval air permit is required for all equipment that discharges contaminants to the natural environment unless the equipment is exempt. Emergency generators must be permitted and in fact the MOE has a specific emergency generator guideline1 that stipulates the environmental compliance requirements and outlines basic requirements of the air permit submission.

Nitrogen oxides (NOx) and noise are the primary contaminants of concern and the MOE makes a clear distinction between an emergency power generator and a general use power generator. For example, the downwind concentration of nitrogen oxides from an emergency power generator is limited to 1,880 micrograms per cubic metre whereas the downwind concentration from a non-emergency power generator is more stringently limited to 500 micrograms per cubic metre. However, if there is a sensitive receptor nearby, such as a hospital, day care centre, school, place of worship, residence, or apartment building, the more stringent nitrogen oxides limit of 500 micrograms per cubic metre limit applies even to an emergency generator.

Prediction of the maximum downwind concentration of air contaminants (exhaust fumes) can be easily accomplished using one of the MOE approved atmospheric dispersion screening models. We recommend that you evaluate environmental compliance early in the planning process in case you have to modify or relocate the generator or generator enclosure, or order a generator with lower emissions.

Environmental noise compliance is established when the noise from your facility satisfies the noise criteria provided by the MOE, or when the noise from your facility blends into, but does not add to, the background noise of the local community. There is no regulation specific to noise and vibration but the MOE has developed a series of Noise Pollution Control (NPC) documents2 that provides limits against which the MOE will assess compliance, or more appropriately the potential to cause an adverse effect.

The MOE provides noise limits for three areas:

A Class 1 area is considered to be within a major population centre where the background noise is dominated by urban hum and road traffic.

A Class 2 area has a low background ambient sound level during the night and possibly early evening (suburban centre).

A Class 3 rural area is dominated by natural sounds with little or no road traffic.

Table 1, extracted from NPC-205 and NPC-232, provides the sound limits for Class 1, 2 and 3 areas. From this table you can see that the noise limit in a Class 1 area at 10:00 PM (22:00) is 47 dBA unless the background is higher. Obviously, you should schedule your emergency generator testing between 7:00 and 19:00 to take advantage of the higher limits and higher background associated with rush hour traffic.

PEN 21 Table 1: NPC Sound Level Limits

The MOE has developed a screening procedure to determine which permit applications require a detailed acoustic assessment report for emergency generator installations.

Screening is based on the separation distance between the emergency generator and the nearest residential receptor (Table 2, Figures 1 & 2). For example, if the generator is located inside a building, such as in a penthouse, and the shortest line of sight distance to the closest residential property line is greater than 20 metres, an acoustic assessment report will not be required.

Table 2: MOE Acoustic Assessment Report Requirements

Emergency Generator
Installed Location
Distance from generator air intake or exhaust louvers, or exhaust stack, to nearest residential property line (metres)
  ≤ 20m >20m <100 m ≤ 60m >60m <100 m
Inside Building (i.e. penthouse) AAR NPC-205    
Outdoors in an Enclosure     AAR NPC-205
AAR- Acoustic Assessment Report required with permit submission
NPC-205 - Compliance with NPC-205 might be required as a condition of operating permit.

Figure 1:
PEN 21: Internal Emergency Generator
Acoustic audit is not required if the distance between an internally housed emergency generator and off-property receptor exceeds 20m.
 Figure 2:
PEN 21: Outdoor Emergency Generator

Acoustic audit is not required if the distance between an outdoor emergency generator (housed in an enclosure) and off-site receptor exceeds 60m.


As a provider of environmental permitting services we have been contacted by property managers wishing to install emergency generators and secure the requisite Section 9 Certificate of Approval (Air) permits. Unfortunately, in a number of cases we were contacted after the emergency generator was purchased and the location sited. We typically find that in and around the GTA and major urban centres, due to the close proximity of neighbouring buildings, the separation distance between the proposed equipment and the nearest on-site or off-property receptors is insufficient. Consequently models predict high nitrogen oxides and high noise impacts at neighbouring properties and in some cases high on-site impact.

Self-contamination occurs when air contaminants or noise from your own equipment comes back into your building through air intakes or open doors and windows. Hospitals in particular present unique challenges since they themselves are sensitive receptors and the MOE requires a detailed self-contamination evaluation to ensure that patients and staff are not adversely impacted. Consequently, it is prudent to evaluate on-site and offsite impact before you complete your design and order your equipment.

Using rudimentary noise prediction calculations and atmospheric dispersion modelling it is relatively easy to predict if noise or combustion by-product impacts will be an issue. The benefits of conducting this assessment before equipment is ordered is that you can work backwards from the noise or air compliance limits to define the equipment specifications.

For example, if nitrogen oxides are predicted to be too high, you can consider cost effective measures such as extending or modifying the exhaust stack, moving the generator further away from the receptor, or if these aren’t possible, consider purchasing generators with low emissions.

Likewise for noise, you can relocate the generator, purchase low noise equipment, purchase noise controls, or custom engineer a solution. Since the cost of retrofitting or replacing equipment can be extremely expensive we suggest a quick compliance check at the planning stage to help minimize capital expenditure and expedite the permit process.

A simplified table outlining the data that will be required and the steps to obtain a permit is available from the Pinchin Emissions Reduction and Compliance Group. 

1 Information for Proponents Applying for a Certificate of Approval (Air) for an emergency generator http://www.ene.gov.on.ca/envision/gp/4131e.pdf