Nyborg commercial dryers
Back when I was younger we went to a laundromat in a vacation town we visited every other year.
They had (and actually have) large prominently red Nyborg Gas dryers.
That brand is long gone but there machines made by Miele and Electrolux sold under that name through time.
This machine is closest to Miele probably though also not at all.
They have an almost Bunsen style burner on the left back of the drum that burns vertically.
In the old place (not the one I linked, though they are the same machines) there was an inspection hole on one dryer you could see the flame through.
In normal operation you might be abled to make out some red glow in the left back and maybe some flame from time to time.
One interesting thing is that those dryers are surprisingly low air flow (at least compared to the Miele machine that ran alongside them) and flame always burned quite red.
So not the best design.
If you increase airflow in a gas dryer you often get better combustion and a bluer flame.
But that greater air volume can pull the flames further.
That would potentially increase the chance of a flame touching the clothing under bad circumstances (as I said, those Nyborg machines would show flames from time to time).
With the burner below or above the drum 2 90° turns are usually used between burner and drum inlet.
Thus if the flame should ever grow to large for any reason, it is unlikely it could make that U-turn.
On these Nyborg dryers as well:
HORRIFIC performance.
Air flow was bad.
You had to use high temperature settings.
The Miele (or even the smaller ELux dryers in my go to laundromat back home) have the amazing advantage to have intense air flow.
Even with medium or low temperature settings you would get fast drying.
High drying temperatures were even and still not terribly extreme.
Those Nyborg dryers heated very unevenly and were running either obscenly hot or very cool.
And took a good 33% longer for the same loads.