Improvement of Interlaboratory Reproducibility for NOx and CO Measurements

Objective

The aim of the research is to define precise measurement techniques for the determination of CO and NOx emissions from appliances burning fossil fuels and to improve the reproducibility of test results among European laboratories, which shall not exceed 15 % relative. (Actual reproducibility lies respectively about 40 % and 25 % for NOx and CO measurement). The research shall improve the CEN technical report CR 1404, which will be amended where needed, in particular to extend its scope to oil fixed appliances.
Measurement and calculation have been carried out to check the influence of the gas composition as well as the nitrogen content in fuel oil: The first results obtained indicate that qualitatively there is a good coincidence between the experimental figures and the model used for the calculation. It is now possible to predict the influence on emissions of gas or fuel oil composition and the corresponding correction formulas have been developed. Sampling has also been fully examined and figures are available on various influences such as sampling point in appliance in chimneys, material used etc. A protocol to measure the sampling line influence has been developed.

Experimental protocols to evaluate the errors due to the analyzers (CO, NOx) have been developed and practical tests have been carried out indicating the range of errors possible in a real situation. Calibration gas bottles from different suppliers are presently tested. Possible drift with time is being checked. This part is not yet finalized. Finally the analysis of the influence of repeatability has led to identification of new error sources.
A GLP document has been written and made available for an intercomparison presently on-going with three different samples (boilers). The GLP document includes details on how to check the measurement instruments and sampling line, the procedures for calibration and testing as well as the detailed method for the uncertainty calculation.

Programme(s)

• FP4-SMT - Specific research and technological development programme in the field of standards, measurements and testing, 1994-1998

Topic(s)

• 01 - Measurements for quality European products

Funding Scheme

Coordinator

Participants (13)