Air content determination

A method for calculating the concentration of one or more of nitrogen dioxide, nitrogen monoxide and ozone in air, the method comprising the steps of:

• activating an equilibrium altering means for changing the equilibrium between nitrogen monoxide and nitrogen dioxide in the presence of ozone and oxygen in an air sample;
• taking at least three readings of the concentration of a first gas selected from the group consisting of nitrogen dioxide, nitrogen monoxide and ozone, wherein at least one of the at least three readings is taken before the changes caused by the equilibrium altering means reach a steady state;
• and
• calculating, on the basis of the at least three readings, the concentration in the air sample of at least one gas selected from the group consisting of nitrogen dioxide, nitrogen monoxide and ozone.

A sensing apparatus for detecting components in atmospheric air as the sensor is drawn up through the atmosphere, the sensor comprising:

• a sensor element;
• shielding means for shielding the sensor element from direct contact with air flow as the sensor is drawn through the atmosphere;
• and
• means for diverting air through the shielding means and over the sensor element as the sensor passes through the atmosphere.

A sensing apparatus, comprising:

• a sensor element;
• means for regulating the temperature of the sensor element by providing heat energy to the sensor element;
• and
• means for calculating the air flow across the sensor element from the amount of heat energy supplied to the sensor element.