Mass spectrometers; Portable gas detecting instruments; Portable gas monitoring instruments; Portable instruments for monitoring oxygen levels in gaseous mixtures; Apparatus for analysing gases; Apparatus for analysing substances in gases; Apparatus for analysing substances; Apparatus for analysing substances in liquids; Apparatus for analysing the composition of air; Apparatus for measurement of gas components in air; Apparatus for the analysis of gas; Apparatus for the testing of gas; Appliances for use in the analysis of gases; Electronic apparatus for the measurement of toxic gases; Electronic measuring apparatus for determining toxic gases; Electronic measuring apparatus for monitoring toxic gases; Gas chromatography apparatus; Gas analysers; Gas detecting apparatus; Gas detecting instruments; Gas detectors; Gas sensing devices; Gas sensors; Gas testing instruments; Instruments for use in gas chromatography; Instruments for use in liquid chromatography; Apparatus for liquid chromatography; Appliances for use in the analysis of liquids; Dipsticks for liquids; Liquid chromatography instruments for scientific use; Pumps for use in liquid chromatography