Flue Patents (Class 122/135.1)
- With flue baffle (Class 122/155.2)
- Having exterior heating flue (Class 122/155.3)
- Having corrugated flue (Class 122/155.4)
- Having undulating flue (Class 122/155.5)
- Central magazine (Class 122/157)
- Circulation tube
- Concentric shell (Class 122/160)
- Exterior drum (Class 122/163)
- Internal water heater (Class 122/165)
- With internal water tube (Class 122/166.1)
- With return fire tube (Class 122/182.1)
- Spiral water conduit
- Standpipe
- Transverse fire tube (Class 122/187)
- Insulated outlet flue (Class 122/164)
- Fluid fuel (Class 122/156)