Air quality measuring device

A circular light guide, comprising:

• an inner portion having a light entering surface through which light enters;
• an outer portion having a light exiting surface through which light exits;
• a coupling boss positioned around the outer portion and provided to protrude upward or downward;
• a rib formed to protrude from one surface of the circular light guide surrounded by the outer portion, the rib being circumferential and positioned radially between the outer portion and the coupling boss;
• and
• a circumferential groove provided between the outer portion and the coupling boss.

An air quality measuring device, comprising:

• an upper case;
• a lower case disposed under the upper case;
• a circular light guide disposed between the upper case and the lower case, having an outer portion and an inner portion, and having a coupling boss positioned around the outer portion to couple with the upper case or the lower case:
• a light source unit positioned on the inner portion, wherein the circular light guide forms a light exiting surface on the outer portion, and includes a rib formed to protrude to one surface surrounded by the outer portion;
• an air quality detector disposed between the upper case and the lower case;
• and
• a controller configured to communicate with the air quality detector and the light source unit,
• wherein the controller is configured to control an operation of the light source unit based on data received from the air quality detector.