1. Portable electronic device enclosed in a housing with an integrated chemical sensor linked to a chemical sensor processing unit and being sensitive to the concentration of a component in a sample of air, further comprising one or more contextual sensors not including chemical, temperature and humidity sensors within the housing, wherein output from the contextual sensors is linked to a local or remote interpretation processor generating a constraint or correlation set transferred to the chemical sensor processing unit for determining a result of a chemical measurement as performed by the chemical sensor.