Los Angeles County Municipal Code § 2203.3 Fire Code

Suitable dust-collection systems shall be designed to collect dust emissions from dust-producing equipment at the point of generation and shall be installed on all dust-producing machinery. Dust-collection systems shall be in accordance with Chapter 5 of the California Mechanical Code. Equipment used in operations that generate explosive or flammable vapors, fumes, or dusts shall be interlocked with the machinery power supply so that the machinery cannot be operated without the dust-collection equipment also operating.

Exception: Closed systems using listed equipment and designed in accordance with manufacturer's recommendations and specifications, where cleanouts are provided in accordance with Section 2203.3.3.

Heating, ventilation, and air conditioning (HVAC) systems shall not be used as the means to collect dusts from localized sources.