A tinted liquid gradually moves through a white viewing window at a pre-calibrated rate. You can read how long the Timestrip® has been active by seeing how far the colour has progressed along the time markers that are printed by the window. When the colour reaches the end of the window, the full time has elapsed and this is the signal to carry out your task or replace a product.nWhen you want to start monitoring elapsed time, activate the Timestrip® by fully squeezing the button between a thumb and finger. An activation line will appear to show that the Timestrip® is working. This line typically appears in a few seconds but can be up to a few minutes in Timestrips® that measure in months and years. Stick the Timestrip® on or near to the product or device it is monitoring and look at it occasionally so you can see when time is up. Dispose of the Timestrip® once the colour has reached the end of the window and activate a new Timestrip® to start monitoring the next product or device.