The sequence of an inspection is a question of what order to inspect the equipment in a system. The two main logical sequences to follow are a co-current flow and a counter-flow approach, but regardless of the type of sequence chosen, it is usually best to initially inspect the outside of a facility. By inspecting the perimeter of a plant, an inspector can see if there are any illegal emissions or odors.

1. Co-current Approach
The inspection of a facility using a co-current approach is conducting the inspection in the same general direction as the flow of the gas stream. The general sequence would be the process, the capture system, the control device, and the stack.
 An inspector may want to use this type of approach when he is unfamiliar with some process details.

2. Counter-flow Approach
An inspection with a counter-flow sequence is conducted against the direction of gas flow. An inspection of this type would generally begin at the stack and continue to the control device, capture system and then the process.
 The advantage to this approach is that an inspector may be able to more quickly identify where an emission problem originates.

3. Other Approaches
In some instances, an inspector may not start with the stack of the process or the beginning or end of a system. If odors are detected outside of the facility, an inspector may want to head directly to the source of the odor. If an inspector suspects illegal tampering with the control device equipment, he may head there directly. If an inspection is a strict, unannounced compliance-type, or if an inspector is very familiar with the process and only has a particular item to deal with, the inspection could start and finish in a different manner.