This depends on several factors, such as: how often the drum is emptied, the rate at which the contents of the drum are emptied, the environmental conditions (temperature, relative humidity, and pressure) and changes in those conditions, exposure to sunlight, and the contents of the drum.
The most commonly used desiccant in drum desiccant breathers is blue silica gel, which allows for an easy visual indication as to when the desiccant needs to be replaced. The units can also be filled with orange silica gel, molecular sieve, activated alumina, or activated carbon.
AGM also sells the aforementioned desiccant in bulk form, including prepackaged replacement amounts of the blue silica gel.
A heavy duty industrial model that holds twice the amount of silica gel is available for larger drums or use in harsh environmental conditions (e.g. tropical).
The units will work in temperatures from -4°F to 131°F.
We recommend a tank desiccant breather.