smoke domain density shrinks with domain size?

Hi. If I use the standard quick smoke I can view and render smoke. However, to fit in my scene, I tried to shrink it down to a candle size, ~1cm. I see that as I progressively shrink the domain size the smoke becomes more and more difficult to see (or render). At 1 cm it’s gone and no amount of jacking up intensities/densities anywhere seems to bring it back. Is this a limit of the code? Am I missing the magic tweak? thanks.