Smell of burning plastics

We usually open windows and turn on the exhaust fan installed on our balcony after we get home. We try to let outdoor air flow in to refresh indoor air and lower the temperature.

Unfortunately, Southern Taiwan has serious air pollution problem, so it is not suitable to open windows sometimes.

We smelled burning plastics when we got home last night, so no open window at all.

It was North wind last night, it must come from the north if there was anything happening.  But I couldn't find anything special from TWEPA Air Quality Monitoring Network (https://airtw.epa.gov.tw/).