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EPA Issues New Guidance on Stack Bypasses

The EPA has issued additional guidance for industry relating to the management of air emissions abatement equipment. This updated guidance replaces the Agency’s previous guidance issued in September 2008. Please note that this guidance note does not apply to sectors subject to the Large Combustion Plant (LCP) regulations of the Industrial Emissions Directive (IED).

During the licensing process, applicants are required to provide all process information, including information on environmental control equipment as specified in the licence application form. Typically, abatement of air emissions is required to comply with the Emission Limit Values (ELVs) stated in the licence. Operating the process without the use of abatement is considered to be operating outside the conditions of the licence. Instances such as these may occur in the event of abatement equipment breakdown or malfunction.

The bypass of air abatement equipment should not happen routinely. In cases where the frequency of bypasses increases, these should be investigated and corrective actions implemented to minimise future occurrences.

The Agency protocols to licensees for the bypass of air emissions abatement equipment are as follows:

Where the licence does not include specific controls to deal with the bypass scenarios, then licensees should develop an appropriate Response Procedure. This Response Procedure should state how the bypass event will be managed in order to prevent the bypass from becoming environmentally significant. Appendix 2 of the protocol provides a framework on the preparation of a Response Procedure.

Where bypasses occur, these shall preferably be monitored.

Bypass events should be recorded. These records should include:

  • The date, start and end-times of the event;
  • The cause of the bypass:
  • The characteristics of the scenario;
  • An estimation of the quantity of the emission;
  • An assessment of its significance; and
  • A description of the corrective and preventative actions taken.


Records of non-significant bypass events should be maintained on-site for Agency inspection and reported in the licensees Annual Environmental Report (AER).

Significant bypass events should be considered as environmental incidents. These incidents should be reported as per licence requirements and in accordance with any Agency guidance on incident categorisation, response and reporting. Appendix 1 of the protocol provides guidance on determining the significance of a bypass.

Where relevant, bypass information must be included in the fugitive emissions assessment report to the Agency and must also be accounted for in the summary of emissions submitted as part of the Annual Environmental Report (AER) and Pollutant Release and Transfer Register (PRTR).


Special Provision in relation to Waste Incineration Directive (WID) Plants

The protocol outlines the additional requirements for incineration and co-incineration plants. Compliance with these requirements is mandatory for licensees in addition to any licence requirements. Licensees are required to develop documented procedures to ensure that the requirements, as outlined below, are implemented on-site.


  • Under no circumstances shall a licensee continue to incinerate waste for a period of more than 4 hours uninterrupted, where any ELV is being exceeded.
  • The total cumulative operational time that ELVs have been exceeded shall not exceed 60-hours over a 12-month period (this limit applies to each incineration unit).
  • In the case of abatement equipment breakdown or malfunction (including bypasses), the licensee shall wind-down or cease operations, as soon as practicable, until normal operations can be re-established.
  • The licensee must keep a documented record of the duration and times of any breach of an air ELV or bypasses of the abatement equipment.

To access the full guidance, follow the link below:

Protocol for the Bypass of Air Emissions Abatement Equipment (2016)

September 2016