A sensor network system for determining a chimney maintenance schedule comprises a sensor unit (16) arranged for placement in or proximate to a chimney (6). The sensor unit comprises at least one sensor arranged to measure a parameter of the chimney (6) and use the measured parameter to generate chimney health data associated with the chimney (6). The sensor unit includes a transmission module arranged to transmit (20) the chimney health data to a remote analysis unit (18). The remote analysis unit (18) is arranged to receive chimney profile data associated with the chimney (6) and to estimate a chimney health level associated with the chimney (6) from the respective chimney health data and chimney profile data. The remote analysis unit (18) determines the chimney maintenance schedule from the estimated chimney health level.

The present disclosure teaches a cleanout opening for chimneys. The cleanout chimney is made of precast concrete, which is a corrosion-resistant material that could last for 50-100 years. The cleanout chimney comprises a door and a frame, wherein, the door and the frame are connected via a pair of arc-shaped slots curved toward the back of the door. The use of arc-shaped slots enables the door to be secured tightly in the frame and can be taken out easily by the user. The front face of the door includes two recessions with a gap in the middle, wherein the gap may function as a handle. Additionally, the arced, curving-toward-the-back shape of the door discourages ash, soot, and debris from accumulating on the inner surface of the door. Compared to a hinged door, the door can be fully removed from the frame, which also facilitates the chimney cleaning process.