Holdover time for de-icing fluids is limited to how many minutes?

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Holdover time is the period after de-icing during which the fluid remains effective in preventing ice from forming before precipitation or dilution ends its protection. In this context, the standard holdover window used in many training materials is about thirty minutes. This reflects typical conditions and common de-icing fluids, where the fluid can still provide protection for roughly half an hour unless new precipitation starts or the fluid becomes contaminated. After that time, the effectiveness can diminish, and reapplication is required to maintain safety. The exact duration can vary depending on the fluid type (I, II, III, or IV), ambient temperature, and the rate of precipitation, so operators rely on manufacturer holdover time charts and local procedures. Shorter durations, like about fifteen minutes, would generally be too brief for common fluids in typical conditions, while longer durations, such as forty-five or sixty minutes, would exceed the standard holdover window used in this scenario.