Flue Gas Dilution fans – your alternative to a chimney
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Flue Gas Dilution fans are the ideal replacement for a commercial gas boiler flue stack. As part of the boiler discharge system they are able to dilute the products of combustion created by gas boilers down to the required safe concentration level of 1% Carbon Dioxide or less, making costly, high level chimney flues obsolete.

What are Flue Dilution fans?

A flue dilution fan is a powerful centrifugal fan which dilutes the waste gas emissions created by commercial gas boilers. They do this by introducing fresh air into the boiler discharge and dilute the CO2 content down to equal or less than 1% concentration, as required for discharging the diluted air outdoors at low level by IGEM regulations. Flue dilution fans are suitable for both atmospheric and condensing type commercial boilers. However, due to the condensation created by condensing commercial boilers, a corrosion resistant fan, such as Airflow’s stainless steel SSDF range, is recommended. Unlike a flued chimney, which would typically need to be many metres tall and in certain areas require planning permission, flue dilution fans only need two metres of ducting from the fan to the outlet to complete a flue dilution system. If LPG or Butane is being used then the air flow rates are increased so to dilute the gases down to the minimum 1% legal level. High quality flue dilution fans come with a differential pressure switch. This acts as a failsafe device as the switch activates in the event of a flue blockage or fan failure and switches off the boiler and gas supply to prevent gas build-up or damage to the system or boiler.

Why would you use a Flue Dilution fan?

You would typically use a flue dilution fan system when it is not possible to build a flue chimney on site due to budget constraints, planning requirements or lack of space. A flue dilution fan enables construction costs for a site to be minimised and for the conspicuousness of the building to be reduced due to the system’s non-intrusive appearance and compact design.

Flue Dilution fan range

Airflow’s range of flue dilution fans is available in five sizes to meet the dilution needs of large domestic, industrial and commercial boilers rated from 80kW up to 650kW input. Each size is available in a standard version (GBDF) and in an enhanced corrosion resistance stainless steel version (SSDF), which extracts up to 1750 l/sec with a system pressure of up to 375 Pa. The GBDF and the SSDF ranges have a maximum ambient temperature of 40°C. Airflow’s GBDF flue gas dilution fans are recommended to be used with atmospheric boilers and waters heaters with an efficiency rating of approximately 75%. This is due to the boiler creating less aggressive condensation which would otherwise corrode and damage the fan. The SSDF fans, thanks to their stainless steel fan cases, have enhanced corrosion resistance and are designed for systems where regulations or the specification calls for stainless steel ducting. This is needed with higher efficiency boilers, as they are likely to produce aggressive condensation which would otherwise corrode and damage the unit. Airflow’s SSDF range, thanks to its stainless steel casing, is also ideal when more corrosive gases need extracting. When designing and installing a flue dilution system using either Airflow’s GBDF or SSDF fan, it is important that attention is paid to the latest editions of the relevant standards and guides. All of Airflow’s flue dilution fans are compliant to the criteria outlined by the Institute of Gas Engineers and Managers regulation IGEM/UP/10 Edition 4 with amendments –March 2016 and February 2017.They are also compliant with Eco design ErP 2015 Regulations