Summary of Rule Amendment Efforts
District Rule 4905 limits NOx emissions from natural gas-fired, fan-type central furnaces with rated heat inputs less than 175,000 Btu/hr and for combination heating and cooling units rated at a cooling capacity less than 65,000 Btu/hr. Unit types include condensing furnaces, non-condensing furnaces, weatherized furnaces, and furnaces installed in manufactured homes.
The District adopted Rule 4905 in 2005 and amended it in January 2015 to lower the NOx emission limit from 40 nanograms/Joule to 14 nanograms/Joule with an associated sell through period and emission fee period to allow manufacturers time to develop new compliant furnaces. Due to the limited number of certified compliant units that would have been available by the deadline dates set in the 2015 amendment, the rule was recently amended in 2018 and 2020 to extend the implementation period to allow the use of emissions fees in lieu of complying with the 14 ng/J limit. Due to the impacts of COVID-19, multiple manufacturers reported manufacturing delays or interruptions in the supply chain, specifically in the development of compliant units for the manufactured homes furnace category. On December 16, 2021, the District Governing Board approved amendments to Rule 4905 to extend the emissions fee option period for manufactured home furnaces for two years, until September 30, 2023.