I/M 240 Overview

I/M 240 Overview:

The I/M 240 stands for the Inspection and Maintenance program that is mandated by the EPA under the Clean Air Act of 1990. Approximately 20 States are scheduled to adopt this form of emission testing beginning as early as January 1995.

I/M 240 applies to states that classify as "Non-Attainment" areas or states that fail to comply with the EPA standards for clean air as specified by the Clean Air Act of 1990. States that do meet the clean air requirements can continue to use the current emission testing procedures (BAR 90) for monitoring purposes.

The I/M 240 testing will be carried out at state run or contracted facilities. The previous dealership and repair station testing will no longer be allowed in these non-attainment locations.

The new form of testing involves a 240 second test cycle where the vehicle is driven loaded on a dynamometer.

The test cycle includes periods of idle, cruise, acceleration and deceleration.

The exhaust gasses are measured using a process called "constant volume total sampling". The amount of HC, CO, CO2 and NOx produced are measured during the test.

Strict parameters for speed and time must be adhered to during the 4 minutes to obtain a valid test.

The measurement for the gasses, during the test cycle is carried out in "grams per mile" as compared to the BAR 90 method of "parts per million". This requires more sophisticated equipment than is currently used by most states in their emission testing. The equipment cost for an I/M 240 testing lane is approximately $250,000.

A second aspect of the I/M 240 test is the checking of the vapor recovery system. The vapor system is pressurized prior to the test cycle and checked for leaks. During the test cycle the purge control system is test for operation.