Sealing smothering method is an important approach to control large fire in channels. This paper experimentally studied the fire behaviors after the sealing in a reduced-scale channel model, considering different initial sealing time under different sealing rates. A series of characteristic parameters, such as the temperature over fire source, mass loss rate of fuel, CO concentration at channel entrance as well as smoke temperature at channel entrance were measured. The results showed that for complete sealing, the earlier the initial sealing time is, the better the fire can be suppressed with a shorter burning duration and lower temperature. However, for incomplete sealing, although the sealing implemented before violent burning stage can reduce the temperature effectively, it causes a much longer burning duration and induces a higher CO concentration at the channel entrance. Especially during violent burning stage, the sealing not only does not restrict fire growth but also exacerbates the channel fire with an extremely high CO concentration at the channel entrance and a longer ceiling flame jet. Besides, as long as one of the channel entrances is not sealed completely, the temperature above the ceiling at channel entrance increases immediately after the sealing, which should be noticed for firefighters during fire rescue.
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