Air content determination

Abstract

An analytical system is provided for determining nitrogen monoxide, nitrogen dioxide and ozone concentrations in air samples. An ultraviolet light source is used to alter the equilibrium between nitrogen dioxide and oxygen on the one hand and nitrogen monoxide and ozone on the other. Dynamic measurement of ozone concentration with time whilst ultraviolet irradiation is pulsed enables each gas concentration to be calculated without requiring input gases to be scrubbed. An apparatus is further provided to provide a controlled flow of gas to a sensor attached to a high altitude balloon whilst sheltering it from the elements and allowing for affects of temperature, said apparatus comprising a shield and a gas conducting means which uses the venturi effect to control air flow or has a hole to allow water to drain without affecting air flow past the sensor.

What is claimed is:  
     
         1 . An instrument for assaying the concentration of one or more of nitrogen dioxide, nitrogen monoxide and ozone in an air sample, the instrument comprising: 
 an equilibrium altering means for changing the equilibrium between nitrogen monoxide and nitrogen dioxide in the presence of ozone and oxygen; and    a first gas sensor for quantifying the concentration of a first gas selected from the group consisting of nitrogen dioxide, nitrogen monoxide or ozone; wherein the instrument is adapted to measure the concentration of the first gas whilst the equilibrium between nitrogen monoxide and nitrogen dioxide in the presence of ozone and oxygen is altered, and to thereby calculate the concentration of at least one of nitrogen dioxide, nitrogen monoxide and ozone in the air sample.    
     
     
         2 . The instrument of    claim 1   , wherein the equilibrium altering means comprises an ultraviolet light source.  
     
     
         3 . The instrument of    claim 2   , wherein the ultraviolet light source is switched on and off periodically.  
     
     
         4 . The instrument of    claim 1   , wherein the equilibrium altering means comprises a means for adding at least one gas selected from the group consisting of nitrogen monoxide, nitrogen dioxide or ozone.  
     
     
         5 . The instrument of    claim 1   , wherein the equilibrium altering means comprises a means for removing one or more of nitrogen monoxide, nitrogen dioxide, ozone or oxygen.  
     
     
         6 . The instrument of    claim 1   ,    2   ,  3 ,  4  or  5 , wherein the instrument is further adapted to measure the concentration of the first gas at a plurality of time points and to thereby monitor the rate at which the balance between nitrogen dioxide and nitrogen monoxide changes in response to the effects of the equilibrium altering means.  
     
     
         7 . The instrument of    claim 1   , wherein the first gas sensor is an ozone sensor.  
     
     
         8 . The instrument of    claim 1   , wherein the instrument is further adapted to allow for the effects of at least one factor, which factor is selected from the group consisting of temperature and pressure, on the equilibrium between nitrogen dioxide and nitrogen monoxide.  
     
     
         9 . 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.    
     
     
         10 . The method of    claim 9   , wherein the equilibrium altering means comprises an ultraviolet light source.  
     
     
         11 . The method of    claim 9   , further comprising the step of switching the ultraviolet source on and off periodically.  
     
     
         12 . The method of    claim 9   , wherein the equilibrium altering means comprises a means for adding a gas selected from the group consisting of nitrogen monoxide, nitrogen dioxide and ozone.  
     
     
         13 . The method of    claim 9   , wherein the equilibrium altering means comprises a means for removing at least one gas selected from the group consisting of nitrogen monoxide, nitrogen dioxide, ozone and oxygen.  
     
     
         14 . The method of    claim 9   , wherein the at least three readings are taken at distinct points in time, and wherein the concentration of the first gas at the distinct points in time is used to calculate the rate at which the balance between nitrogen dioxide and nitrogen monoxide changes in response to the effects of the equilibrium altering means.  
     
     
         15 . The method of    claim 9   , wherein the at least three readings are of ozone concentration.  
     
     
         16 . The method of    claim 9   , further comprising the step of allowing for the effects of at least one factor, which factor is selected from the group consisting of temperature and pressure, on the equilibrium between nitrogen dioxide and nitrogen monoxide.  
     
     
         17 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 9   ,    10   ,  11 ,  12 ,  13 ,  14 ,  15  or  16 , wherein the gas is selected from the group consisting of nitrogen monoxide, nitrogen dioxide and ozone.  
     
     
         18 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 9   , wherein said program is disposed on a tangible medium.  
     
     
         19 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 10   , wherein said program is disposed on a tangible medium.  
     
     
         20 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 11   , wherein said program is disposed on a tangible medium.  
     
     
         21 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 12   , wherein said program is disposed on a tangible medium.  
     
     
         22 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 13   , wherein said program is disposed on a tangible medium.  
     
     
         23 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 14   , wherein said program is disposed on a tangible medium.  
     
     
         24 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 15   , wherein said program is disposed on a tangible medium.  
     
     
         25 . A computer program which, when loaded onto a computer, is adapted to calculate the concentration of a gas in an air sample in accordance with the method of    claim 16   , wherein said program is disposed on a tangible medium.  
     
     
         26 . 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.    
     
     
         27 . The sensing apparatus of    claim 26   , wherein the means for diverting air comprises a gas conducting member shaped to provide a pressure differential across the shielding means and to cause air to move through the shielding means.  
     
     
         28 . The sensing apparatus of    claim 27   , wherein the gas conducting member is shaped to provide a low pressure region at an entry to the shielding means and thereby draw air through the shielding means into the gas conducting member.  
     
     
         29 . The sensing apparatus of    claim 27   , wherein the gas conducting member comprises a flow restricting member for diverting air that flows through the gas conducting member in use into the shielding means.  
     
     
         30 . The sensing apparatus of    claim 29   , further comprising an aperture adapted to allow water or ice to flow out of the gas conducting member.  
     
     
         31 . 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.    
     
     
         32 . The sensor apparatus of    claim 31   , further comprising a means for measuring the temperature of the sensor.