For hazardous air pollutants (HAPs)

For hazardous air pollutants (HAPs), process equipment vented to the air
emissions–control system shall suspend operations immediately to prevent
uncontrolled air emissions from escaping into the atmosphere. Supplier shall
install and maintain an automatic shutdown system in which any HAP-emitting
operations are ceased when the flow from these operations is diverted away
from the air emissions–control system—for example, to a bypass line—
regardless of circumstances or whether the air emissions–control system is shut
down or fails.