Beware of falling NOx

Nitrous Oxide emissions are one of the acceptable methods of evaluating pollutants from modern boilers and therefore are used as a benchmark to evaluate the carbon footprint of heating plant when designing new buildings. Unfortunately certain important problems have emerged with the assessment of these noxious emissions.

Nox forms an integral part of the BREEAM calculation and as such is an important factor when consultants are selecting heating products for a particular project. The lower the Nox emissions the greater the carbon credits being available to the designer. It is therefore most important that boiler manufacturers strive to produce equipment that offers the lowest Nox emissions possible in order to comply with legislation and gain a commercial advantage.

Nox emission levels are derived from the actual raw emissions of an appliance; they are then subjected to a calculation that results in an emission level.

There are many standards to which a boiler can be approved; unfortunately all of these standards use different methods of calculating Nox emissions. Generally the older standards result in considerably more favourable or lower Nox emissions, whereas the very latest standards tend to result in apparently higher emissions.

This situation can result in older, technically less advanced boiler plant apparently offering better emissions than new purpose designed product. This is obviously not the case and the user, designer and installer must be aware of this major anomaly.

To further demonstrate this problem, if we take the raw Nox emissions from a single boiler, apply the equation from an early standard then compare it to the equation from a modern standard, the variation can be as much as 3:1.

This would have a massive influence on the BREEAM calculation.

It should now be obvious that the publication of Nox figures can be used to exaggerate the performance of a particular product, at present manufacturers are quite free to quote Nox levels to any standard they wish, unfortunately selecting a standard that results in apparently lower Nox levels seeks to gain advantage over possibly superior products.

It is important that everyone be made aware of this anomaly. When comparing boiler plant, be careful to ensure that the published Nox emissions are to comparable standards. To this end Mikrofill are now quoting Nox emissions according to three of the most frequently used standards.

For the sake of clarity, Mikrofill are campaigning that all manufacturers should publish their Nox emissions to the same standard.