Anyone knows a gas that is denser/heavier than air at room temperature (at 20ºC, add or substract 5ºC) and which isn't lethal to humans? (preferibly it gotta be translucent, but even more important, it gotta be cheap and safe for people to walk through it as long as they keep their nose well above it in order ot breath real air or only sink their noses in it as much as they can hold their breath)?

If they trip over, they will die.

Ar, Xe, SF6, possibly CO2. As JC implies, the danger is oxygen displacement. It's like tightrope walking without a net. Tightrope walking is not lethal, but tightrope falling is.

Can you give us an idea of the application? If people are going to walk through it, are you building a facility that can keep the gas from dropping through cracks or vents in the floor? Are you thinking it will slow people down as they walk through it? Do you mean transparent instead of translucent? Do you want people to see the gas or just have light shine through it?

CO2 is toxic, Ar is only marginally denser than air (about 33%). SF6 and Xe are not what most people consider cheap.

In any event, diffusion will mix the gas into the air and reduce the oxygen concentration in the breathing zone (so they will get light-headed and fall over and die).

Xe is an anaesthetic at or around atmospheric pressure.

 

If you had money to burn you could use a premixed 20% O2 in SF6 mixture, but God help you getting any sort of license to play with this at a public event.

How about Freon? I used to launch model rockets powered by Freon, it is very dense and does pool in low areas...

There are lots of "freons" and they are all more or less toxic.

In any event, none of them is oxygen.

How about Freon? I used to launch model rockets powered by Freon, it is very dense and does pool in low areas...

Ah so you are the cause for the ozone hole. Just kidding but this family of organic gases isn't really healthy either.

There are lots of "freons" and they are all more or less toxic.

In any event, none of them is oxygen.

 

 

Ah so you are the cause for the ozone hole. Just kidding but this family of organic gases isn't really healthy either.

 

 

I understand you can't breath freon, I didn't know they were toxic, one of the main things they said about the rockets was that the freon was harmless. I can't remember the freons number, for some reason 22 sticks in my mind but I'm not sure. I was thinking that mixed with oxygen it would be breathable. I remember testing a lot of rockets indoors, strapped down so they couldn't move, they didn't harm me...

Argon is more or less affordable and non-toxic, but only 1.784kg/m³. Mix with 20% oxygen for breathing. Krypton is denser but more expensive.

 

CO₂ is nearly non-toxic over a limited time. 1562kg/m³. Mix with 20% oxygen as well. In calm air it stays separated, but will mix when people walk through, as any gas.

 

Freons would have been nice... But all that contain chlorine atoms are forbidden, we have only the ones with fluor, and these are expensive.

 

Depending on the effect sought, could you use artificial mist instead? Available for shows, rather dense, safe.