Abstract: A method performed by a system controller and evaluating a manhole event occurring in a duct-manhole system. The method includes estimating a size of the manhole event occurring in the system or estimating relative contributions to a fire of at least two of oxidative decomposition, pyrolysis, plasmatization, and flammable gas accumulation. Optionally, the method may include notifying one or more users and/or altering a rate of atmospheric turnover in the duct-manhole system.

Abstract: A method that includes obtaining a sensor reading from a sensor installed inside an underground vault and determining whether the sensor reading is indicative of an alarm state. When the sensor reading is indicative of the alarm state, the method obtains at least one new reading and determines whether the sensor reading includes sensor drift based at least in part on the at least one new reading. The alarm state is established when the sensor reading is determined not to include sensor drift. The sensor drift is removed when the sensor reading is determined to include sensor drift.

Abstract: A system that includes a gas sensor, a fresh air flow controller, a sample flow controller, and a system controller. The fresh air flow controller is configured to deliver fresh air to the gas sensor. The sample flow controller is configured to deliver a sample to the gas sensor. The system controller has a processor connected to memory storing instructions that are executable by the processor. When executed, the instructions cause the processor to determine an intermix ratio of the sample to the fresh air, instruct the fresh air flow controller and the sample flow controller to deliver the fresh air and the sample, respectively, to the gas sensor in accordance with the intermix ratio, and receive a sensor reading from the gas sensor after the fresh air flow controller and the sample flow controller have adjusted the fresh air and the sample, respectively.