Is ground level ozone invisible?

[Cowhide]

Ok, so it's 105 outside, and the NWS issued a smog advisory for SoCal. Inland empire.

As the air is currently 134ppb (Unhealthy for sensitive groups/Unhealthy)
but as I'm looking out my window, I don't see the smog. Usually when I know there's smog it's a very thick brown haze that you cannot see the hills at all..but I can see the hills fine, and the buildings, with maybe just a hint of a white haze. Just a hint.

So what's going on?

Is the brown haze "particulate matter" and "white" ground level ozone?

In other words, could the air quality really be bad, as you're doing outdoor activity, and not even know it?

[Aslkahuna]

Yes-Ozone is an isotope of Oxygen and hence as visible to the human eye as O2. The brown cloud is usually caused by oxides of nitrogen which are also photochemical products and which have a brownish coloration. Both are usually found together. The white haze is probably suspended salt particles from the nearby ocean or it could be sulfate aerosols.

Steve

[I-wall]

Ozone is a pale blue gas, but the concentrations of ozone that occur naturally are so low that it would be invisible to the human eye. The only way you would know if there is ozone is by the smell...the human nose can detect ozone at concentrations as low as 0.01 ppm.

[jasons2k]

I always wondered...even though it is bad for your lungs, does ground-level ozone also block UV rays?

[I-wall]

IMO, there isnt enough ozone at ground level to block UV light.