Class I, II, and III are written reports and will include recommendations for the next appropriate inspection type and schedule.
Hoffmann’s Inspection classifications were developed using Chimney and Stack Inspection Guidelines, edited by Bernhardt H. Hertlein, published by the American Society of Civil Engineers, 2003.
Warning: Many chimneys may contain hazardous materials such as asbestos, lead-based paints, and toxins.
Class I inspections are routine (not exceeding 2 years), visual inspections, using binoculars or spotter scope from the ground or any close vantage point.
It is best to perform a Class I chimney inspection during shut-down to allow access for a full-height inspection of the liner and annular space. While the chimney is off-line a close-up visual inspection can be made of sections of the chimney accessible by all permanent access components, ie: ladders, platforms.
Class II inspections should be performed every 2 to 5 years. A Class II inspection must be performed during a chimney shut-down and includes the scope of a Class I inspection, plus a full-height interior and exterior inspection.
Additional scope may include:
- Full or partial thickness core samples of concrete or brick
- Nondestructive assessment of thickness and weld condition on a steel stack and liner
- Nondestructive assessment of FRP liners
- For concrete or brick chimneys, installing crack monitoring equipment
Class III inspections are not routine and are primarily performed with significant degradation of any structural component has occurred or when the chimney has experienced an unusual event. Examples of unusual events: earthquake, hurricane, tornado strength winds, explosion, implosion, fire, overheating, or flooding.
A Class III inspection should also be performed before any significant structural modifications to the chimney wall or liner that change performance and/or applied loads.