Although this terminology can be confusing, the difference between these two different levels of inspections, including when and where they are appropriate, is actually quite simple. A Level I inspection is your yearly, routine inspection. Code calls for your chimney to be swept annually.
This level of inspection requires the service technician to inspect all of the readily accessible areas of the chimney, appliance, flue, and connectors. There are thirty three points that are a part of the inspection, and although these points are required for a Level I inspection, the list is not exhaustive.
Sometimes, a service technician is required to go above and beyond the minimum requirements of a Level I inspection in order to determine certain factors concerning the chimney, such as what type of flue system is appropriate for a specific chimney or appliance, or whether or not there is indeed damage at any point in the flue system. These problems may require the service technician to get onto the roof to inspect the top of the chimney or execute any other number of services above and beyond the typical Level I inspection requirements.
A Level II inspection is necessary when a question regarding a chimney cannot be answered by merely inspecting the easily accessible areas of the chimney. Weather conditions that may have caused damage usually require a Level II inspection. A Level II inspection encompasses all aspects of a Level I inspection, the extra steps are merely that, extra.
The sweep will have to move about the house in order to complete a Level II inspection. The roof top, the chimney top, the basement or crawlspace, and the attic will all be inspected. This type of inspection is generally utilized for homes that are on the market, and are required before a home can change hands.