Mixtures containing reactive and corrosive gases (e.g. formaldehyde) have limited shelf life in standard, untreated cylinders because the gases react with the internal surface, changing the composition of the mixture. This mixture instability also means that the measurement uncertainties for reactive components are wider than for stable ones.
Instability of calibration gases containing reactive gases can cause problems because
- they have limited shelf lives so need to be replaced more frequently / before the cylinder has been used up, which usually means extra costs for the customer
- shorter shelf lives and limits on the amount of these components that can be added to a mixture can hamper research into more challenging gases, e.g., ozone precursors and hydrogen, which are key for environmental monitoring and carbon-neutral fuel development
Treated cylinders not only increase the stability of mixtures, but also offer lower uncertainties, providing confidence in your measurements.