a) providing a portable gas detection device and at least one gas exchanger for implementing in the indoor space, wherein the portable gas detection device can be carried by a user, and the portable gas detection device comprises a main body, and the main body comprises at least one inlet, at least one outlet and a gas detection module, the gas detection module is disposed in the main body and comprises a base, a piezoelectric actuator, a laser component and at least one sensor, wherein the piezoelectric actuator, laser component and the at least one sensor are accommodated in the base, and the at least one sensor includes a particulate sensor, the at least one gas exchanger is allowed to inhale an outdoor gas, purify and filter the inhaled gas, and introduce the inhaled gas into the indoor space, wherein an air pollutant in the indoor space is exchanged and exported out to the outdoor environment;

b) disposing 1 to 50 gas exchangers within the indoor space, wherein the at least one gas exchanger has an exported airflow rate ranged from 200 clean air delivery rate (CADR) to 1600 CADR, and the indoor space has a volume of 247.5˜1650 m3; and

c) remotely controlling at least one of the gas exchangers to enable filtration, purification and gas exchange procedure by the portable gas detection device, as the portable gas detection device detects an air pollutant in the indoor space in real time, to reduce the air pollutant in the gas in the indoor space to a safe detection value within 10 minutes, so that the air pollutant in the indoor space can be exchanged and purified.