The District's Wood Burning Fireplaces And Wood Burning Heaters Rule (Rule 4901) is the most stringent rule in the nation and significantly reduces emissions of direct PM2.5 emissions when and where those reductions are needed most, in urban residential areas during periods of atmospheric stagnation.  The Rule collectively reduces emissions of 5.1 tons-PM2.5/day.  Amendments to the rule also lowered the curtailment threshold for non-registered wood burning devices from 30 to 20 ug/m[3], significantly lower than any other rule in the nation.  The below discussion provides further clarification and summarizes information included in the staff report prepared during adoption of Rule 4901.

Registration of Certified Wood Burning Devices
Rule 4901 allows certified wood burning devices to be operated during days when the pollutant concentration levels are forecast between 20 ug/m[3] and  65 ug/m[3] as long as the device is registered with the District and operates in accordance with Rule 4901 as follows:

   1. Wood burning devices must be inspected by a Qualified Wood Burning Heating Professional and receive a certification prior to receiving a registration from the District.  
   2. Qualified Wood Burning Heater Professionals must meet the following requirements:
         a. Maintain a professional certification as outlined in Rule 4901. 
         b. Apply to the District and be placed on a list of approved Qualified Wood Burning Heater Professionals.
   3. Qualified Wood Burning Heater Professionals are required to conduct a thorough and rigorous review and evaluation of the wood burning device before providing a certification to the District.
   4. Once the Qualified Wood Burning Heater Professional completes the inspection and provides a certification for the device, the registration is issued with a set of operating conditions for compliance with Rule 4901.  This includes requirements for the wood burning device to operate in compliance with Episodic Wood Burning Curtailments issued by the District and prevents burning of any prohibited fuel types as identified in Rule 4901.  
   5. Registrations are valid for a period of up to three wood burning seasons from the date of registration issuance; however, certificates can be disqualified if the District finds the wood burning device is operated in violation of the requirements of Rule 4901.
   6. Upon completion of the three-season period, the registration of the unit will need to be renewed and again pass an inspection by a Qualified Wood Burning Heater Professional.   

Due to the stringent requirements for registering a wood burning device, it is expected that a limited number of residents will take advantage of registering their wood burning devices.   

During the rule 4901 development process, the District performed a worst-case-scenario analysis of estimating the potential increase in emissions from the transition of high-polluting uncontrolled devices to clean certified registered devices operating when pollutant concentration levels are forecast between 20 ug/m[3] and  65 ug/m[3] (Appendix B - Emission Reduction Analysis).  In this analysis, the District assumed that 24% of all existing high polluting wood burning devices in the Valley would transition to clean certified units, all 24% of devices would register these devices with the District, and all 24% registered devices would operate on days when PM2.5 concentrations were projected to be between 20 and 65 ug/m[3].  Based on this scenario, the District estimated a total increase in emissions of only 0.22 tons per day (tpd).  

The above mentioned scenario is based on a worst-case and unrealistic scenario. The assumption that all wood burning devices would transition to clean certified wood burning devices was solely to calculate the absolute worst case scenario.   Through the District's Burn Cleaner incentive program, over 80% of devices have been replaced with natural gas-fired units.  This is indicative of the Valley-wide trend of the transition of high polluting devices to clean units.  Furthermore, as discussed earlier, only a minority of EPA clean certified devices are expected to register due to the stringent registration requirements under Rule 4901.  A more reasonable, but still conservative, assumption would have been to assume only 20% of the 0.22 tpd emissions would occur because of the aforementioned transitions (still assumes that all clean certified devices register with the District).  Taking these more accurate factors into account and applying them to the previous highly conservative analysis results in a more representative emission increase of 0.044 tpd (0.22 tpd x 20% = 0.044 tpd) when air quality is forecast to be between 20 and 65 ug/m[3].  This amount is insignificant with respect to PM2.5 concentrations and does not take into account the 3.33 tpd of direct PM2.5 emissions reductions from the lowering of the curtailment threshold, and the 2.04 tpd reductions from the transition to the cleaner certified units.   

The combination of stringent requirements that must be met to register a wood burning device, including all associated costs for receiving a registration, increased transition to natural gas-fired units instead of wood-fired units and the de minimis amount of emissions resulting from the few units that can be used when PM2.5 is forecast to be between 20 and 65 ug/m[3]  will result in an insignificant impact during this period and Rule 4901 as a whole results in significant emission reductions.  
