Instructions for Using Diesel Engine Screening Risk Assessment Tables

This page last reviewed November 26, 2008


Use these steps when calculating a screening health risk assessment score for a facility with stationary diesel engines.


Step 1

Before beginning your analysis, determine the Load, Engine Size, Emission Factor, Distance to Nearest Receptor, and Annual Hours of Operation for each of your engines. The district will help you determine the Urban/Rural Option.

Step 2

Please choose the load that most closely matches the average load for the engine during testing (either 50 or 75% load). Then click on the table with the engine size that is closest in size to your engine.

Step 3

Find the matrix that corresponds to your emission factor (either 0.01, 0.15, 0.40, 0.55, or 1.0 g/bhp-hr). If you do not know the emission rate of your engine, use 1.0 g/bhp-hr. 

Step 4

Find the row that corresponds to the correct number of hours of operation (on the left of the table), and the column with the correct receptor distance (between 20 and 1600 meters) to calculate the risk from that engine.

Step 5

Repeat these steps for the other engines and sum the results to get the total facility risk.

Step 6

Work with local air district to determine next steps.


Example Calculation:

Step 1:
Engine load = 50% (estimated)
Engine size = 180 hp (maximum rated horsepower)
Emission factor = 0.40 g/bhp-hr (certified emission rate at maximum load - assume 1.0g/bhp-hr if unknown)
Annual hours of operation = 29 h (includes all operating hours, including maintenance and testing,
except actual emergency hours)
Distance to nearest receptor = 53 m (measured from the engine to the nearest residential or commercial receptor)

Step 2: Since the engine primarily performs at minimal load during testing, we will use the 50% load tables. The 180 hp engine is closest in size to the 175 hp engine, so we will use the 175 hp table for this example.

Step 3: Click on the 175 hp table and find the matrix that corresponds to 0.40 g/bhp-hr.

Step 4: Identify the row that corresponds to 30 hours (closest to 29 hours) and read across until you find the risk value that is directly under 50 meters (closest to 53 meters). The maximum estimated risk is 8 per million.

Step 5: Repeat as necessary and sum the results to get the total facility risk.

Step 6: Submit results of screening risk calculation to the local air district upon request.

A copy of the MS Excel spreadsheets is available: (50% load) and (75% load).

Because some receptors may be located closer to the engine than the point of maximum impact (the PMI or area of highest risk), we have created tables that retain the higher risk numbers for distances closer than the PMI in order to ensure that these screening tables are still health conservative (50% modified) and (75% modified).


Back to Screening Risk Spreadsheets
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