The filter for the HAKKO FA-400 and HAKKO 493 Smoke Absorbers (PN: A1001) is rated to be able to absorb approximately 4g of noxious components per filter. The typical weight of a new filter is 12g, so once this weight reaches 16g, the filter is saturated and should be replaced.
Keep in mind that how quickly the filter becomes saturated depends on the amount of use and the amount of soldering work being done. Under normal operating conditions, the filter should typically be replaced once per month, or if dust is sticking to the front of the filter and it is no longer absorbing the smoke well.
These filters are not washable so do not try to clean the dust with water. Do not use compressed air to blow the dust out as you will likely blow out the other noxious components that the filter had previously absorbed.
Please see the attached document for additional information on the performance of the A1001 Filter and its ability to absorb smoke over time.