What is the maximum allowed diurnal emissions from an evaporative system in California?

The maximum allowed diurnal emissions from an evaporative system in California is set at 0.2 grams per hour. This standard is established to help regulate and minimize the amount of volatile organic compounds (VOCs) that escape into the atmosphere from vehicle fuel systems when they are not in operation.

Diurnal emissions occur as temperature changes throughout the day, causing the fuel in the tank to expand and contract, which can lead to emissions moving into the atmosphere. By maintaining strict limits on these emissions, California aims to reduce air pollution and protect public health. A limit of 0.2 grams per hour is seen as a significant achievement in emissions control technology, reflecting the advancements made in automotive evaporative system designs.

It’s important for inspectors to understand these standards to ensure vehicles are compliant and contribute to the overall effort to improve air quality.