When PSI hits 700, work from home

When PSI 300 is very unhealthy, when PSI above 400 is hazardous, life goes on. No emergency will be declared. Put on your masks and soldier on to keep the economy going. For those vulnerable groups, put on your H95s when outdoor.

At what level of PSI would there be an emergency declared, 700 or 800? Or is it 700 on an hourly reading or 700 on the 24 hour average? Would haze kill at 700 or 800?