Examples include measurements of:
- exhaust emissions from automobile and aircraft engines;
- emissions from chemical and combustion processes;
- air quality in rural and urban areas and work place atmospheres;
- natural gas for determination of calorific value and relative density.
This Report provides a short description of the National Physical Laboratory's Primary Gas Standards Facility, discusses the methods used to prepare and certify secondary gas standards in a manner which is traceable to Primary Standards, gives the uncertainties assigned to the concentration values of these secondary standards, where this is required. The Report covers gas standards with concentration ranges of greater than 1ppm. Other techniques may be used for standards which have concentrations lower than this.