INTRODUCTION

Numerous scientific studies show that indoor of homes and businesses are the source of potentially harmful substances called indoor air pollutants. They come from variety of sources. Indoor levels are often much higher than outdoor levels and most people spend the bulk of their lives indoors. This is the biggest single contributor to health-damaging indoor air pollution in cities. Regulation of fumes emited by vehicles and factories has something to offer by way of solution, but what is needed most is increased health by better housing and by proper planning of cities and roads. The problem cannot be solved simply by academic laboratory research. An air pollutant is seldom present in outdoor air on its own and normally the air contains a mixture of several pollutants. The composition varies according to the prerequisites. It has not yet been determined how the various substances affect human beings when they interact. Main groups of pollutants were subjects of our special interest as nitrogen oxides, volatile organic compounds, carbon monoxide and sulphur dioxide.

INDOOR CHEMICAL POLLUTANTS

Nitrogen Oxides
Nitrogen monoxide and nitrogen dioxide are mainly produced by combustion at high temperatures and are formed by reactions between nitrogen and oxygen. Both nitrogen in the fuel and nitrogen in the air participate in reaction, NO is further oxidized and transferred into NO2 in the atmosphere. Nitrogen dioxide is the most toxic of the nitrogen oxides and is the most important from view-point of health. In Slovakia it is possible to assess that about 40 % of nitrogen oxides emissions originates from road traffic, about 50 % from combustion and about 10 % comes from industrial processes. During recent several years the emissions of nitrogen oxides have increased. There is great difference between annual average value of nitrogen oxides in the countryside and in the big cities. Outdoor average concentration level of nitrogen oxides are shown in figure 1. Nitrogen oxides are also formed during lightning storms and are said to be responsible for part of the continual increase in acidity of rainfall.

Figure 1: NOx concentration level dependences

People are mainly exposed to indoor nitrogen oxides. Indoor air can be contaminated by the use of gas for heating and cooking appliances. The most important indoor source of nitrogen oxides is gas burning in the kitchen.