PM2.5 Tiering Tool - for Exceptional Events Analysis
This tool displays daily PM2.5 concentrations, along with tier levels based on the methodology described in the PM2.5 Wildland Fire Exceptional Events Tiering Document (pdf) . You can use the tier level to determine the evidence needed to establish a clear causal relationship in a wildland fire PM2.5 exceptional events demonstration.
For questions about tool functionality, please contact Loren Fox at fox.loren@epa.gov.
For questions regarding tiering thresholds at individual sites, please contact the appropriate Exceptional Events Regional Coordinator.
Tier Thresholds in this tool are:
1. Based on the most recent, complete 5-year period 2020-2024. This tool does not have a minimum data completeness requirement. If a site has less than five years of data, please work with the corresponding EPA regional office to determine the appropriate tiering analysis.
2. Calculated at the site level. Specifically, we use site-level aggregated daily values consistent with PM2.5 NAAQS data handling [see section 3.0(d)]. For identifying which site-days to exclude from the tier threshold calculations, we consider the raw data record for all monitors at a site. If any hour of the day at any monitor at the site has an R (Request Exclusion) flag or a fire-related I (Informational) flag, then we exclude the site-level aggregated daily value from the tier threshold calculations. Fire-related I flags include IT (Wildfire - U.S.), IF (Fire - Canadian), IG (Fire - Mexico/Central America), IH (Fireworks), IM (Prescribed Fire), and IP (Structural Fire).
3. Based on the lesser value of either (a) the most recent 5-year month-specific 98th percentile for 24-hour PM2.5 data, or (b) the minimum annual 98th percentile for 24-hour PM2.5 data for the most recent 5-year period with all R flagged and fire-related I flagged days excluded. Tier 1 demonstrations are appropriate for 24-hour PM2.5 greater than or equal to 1.5 times the threshold determined above, Tier 2 demonstrations are appropriate for 24-hour PM2.5 greater than or equal to the threshold but less than 1.5 times the threshold, and Tier 3 demonstrations are appropriate for 24-hour PM2.5 less than the threshold. See the PM2.5 Wildland Fire Exceptional Events Tiering Document for further details.
Data Flags:
1. In the context of this tool, "flagged data" are data in AQS that have been flagged by the State or local agency as having been impacted by any of the wildfire event types in AQS (e.g., IF, IG , IM , IT, RF, RG, RM, RP, RT).
2. Additional information regarding how data are flagged in AQS and differences between R and I flags:
- AQS Exceptional Events Tutorial
- Updated Exceptional Events Rule FAQs (see Section A)
Data Refresh Schedule: The data for this tool and the site-level tiering thresholds file below will be refreshed every two weeks and each will include a date stamp. With each bi-weekly update, any new data submitted to AQS will be reflected in the tool, and the tiering thresholds will be recomputed so that if any new R flags or fire-related I flags have been applied since the last data refresh, then those data will be excluded in the calculation of the tiering threshold in accordance with the tiering methodology.