Just to prove my point, a little history from the TNRCC website. August 5, 1972 was a nasty day in Houston,TX. the following ozone readings were recorded :11AM:130PPM, noon: 250PPM, 1PM: 300PPM, 2PM:315PPM, 3PM:425PPM, 4PM:320PPM, 5PM:200PM, 6PM:205PM, 7PM:180... Login to read more.