According to 29 CFR 1910.164(c), it is the employer’s responsibility to maintain all fire-detection systems in an operable condition, except during maintenance and repair work.  You must ensure that these systems are tested and adjusted as often as necessary to maintain reliability and operating condition.

The frequency of the tests and cleaning cycle must be determined in part by facility conditions, such as dust, as well as manufacturer recommendations.  Conditions such as the amount of dust, dirt, or other particulates may vary widely from one facility to another and therefore vary the maintenance cycle.
Factory-calibrated detectors do not need to be adjusted after installation, unless recommended by the manufacturer or service representative. However, trained personnel knowledgeable in the operation and function of the system must perform testing, cleaning, and maintenance of fire-detection systems.

You must also ensure that pneumatic and hydraulic-operated detection systems installed after Jan. 1, 1981, are equipped with supervised systems.