The cause of the failure of the common evaporator frosting or temperature sensor circuit, the installation position of poor ventilation and dirty filter indoor machine.

引起该故障的原因常见为蒸发器结霜或温度传感器断路，室内机安装位置通风不畅以及过滤网太脏等。

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Tokyo has shown that mass-transit systems need not be a poor or dirty option.

ECONOMIST: Driving

Poor piercing hygiene practices such as reusing dirty equipment or not washing ones hands or changing gloves may also enable infections to be spread.

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The global burden of illness owing to dirty water, bad or non-existent sanitation and poor standards of hygiene is remarkable, according to the studies cited by Mr Rijsberman.

ECONOMIST: Economics focus