Significant changes to the 2018 International Mechanical Code
The 2018 Significant Changes guides are available for the International Building, Residential, Fire, Plumbing, Mechanical and Fuel Gas Codes. This valuable series can help any code user save time by zeroing in on the most critical changes in the 2018 International Codes. The Code Council’s technical experts provide summaries, analysis and graphics for these changes making them clear and easy to understand.
2018 International Mechanical Code
A modification to Section 404.1 (Mechanical Ventilation of Enclosed Parking Garages) states that the code text was rewritten to clarify the intent with regard to “intermittent” operation.
This code section has been misinterpreted regarding intermittent operation. No technical changes were made, rather the text was rewritten to make it clear that the garage exhaust system can never shut off completely. The exhaust is either full-on all of the time, or it is allowed to be cycled between full-on and minimum-on by CO and NO2 detectors. “Intermittent” operation implied that the system could shut off completely, which was never the intent. The detectors determine when the exhaust system goes from standby (minimum rate) to the full-on rate. If the system is operated in a continuous mode without detectors, then it would operate at the full-on rate continuously.
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