The Interster Formaldehyde Indicator is used in low temperature steam formaldehyde (LTSF) sterilisation up to 73°C. This is an effective method of sterilisation of heat sensitive medical devices that are not suitable for steam sterilisation. Correlated to inactivation for formaldehyde, the indicator monitors the critical parameters of the sterilisation process. The ink will change from pink to green under the correct circumstances.