A gas sensor for a handheld device is assembled in a cavity of the handheld device. The gas sensor comprises a sensing chip, a circuit board and a gas channel. During operation, when a to-be-sensed gas is blown to a first sub-channel away from a gas inlet via a second sub-channel in the gas channel adjacent to the gas inlet, a gas pressure is weakened by the channel, so that the gas pressure of the first sub-channel is lower than the gas pressure of the second sub-channel. Therefore, dust and other tiny substances are prevented from entering the handheld device, and the damage to the sensing chip caused by the gas pressure during blowing can also be avoided.一種應用於手持式裝置的氣體感測器，係裝設於手持式裝置容設有麥克風的腔體中，包含：感測晶片、電路板以及氣體通道。在操作時，待感測氣體經由氣體通道中靠近氣體入口的第二子通道吹往遠離氣體入口的第一子通道時，氣壓受上述通道設置而削弱使第一子通道的氣壓小於第二子通道的氣壓，不僅避免灰塵及其他微小物質進入機體，亦能避免吹氣時氣壓對感測晶片造成損害。
