The development of natural gas fields in the North Sea has 
introduced a new type of heating of homes in northern Europe and 
also a new type of local pollution source. Using natural gas causes
concern about issues regarding emissions of pollutants such as 
nitrogen oxides, NO and NO2, often collectively referred to as NOX.

The study is based on data collected from November 1987 to April 
1988 in the village of Åkarp in southern Sweden. Each home in the 
area was heated by its own natural gas furnace. The question has 
been how to reveal the contribution of  NOX due to the furnace.

Another issue of great importance is the total amount of NOX 
emitted to the atmosphere, and of special interest is the extreme 
values. Here the Generalized Pareto Distribution is used as a
model. It is investigated how an underlying normal error caused by 
the measuring system will affect the distribution.

Further the quantiles in the Generalized Pareto Distribution 
disturbed by a normal error have been investigated. Methods have 
been developed so that these quantiles can be expressed in terms of 
the well known standard normal quantiles. The observed quantiles can
then be related to the true quantiles and thus the influence of the
measurement errors can be illustrated.