| 摘要 |
A novel air filter and timer for alerting persons responsible for changing or cleaning the air filter that it is time for servicing. An audible alarm is provided on the timer to emit a prolonged or intermittent audible alarm to indicate the need for servicing. The alarm can be incorporated into the filter or made separately and affixable to an air filter. The alarm sounds after a set time period to alert the user to change the filter.
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