I adapted Manfred's instructions regarding his lens/lighting technique.
Originally I used my 180 macro lens simply because that's what was mounted on the camera...Dah.
With a series I ran today in a "not dark enough room" using homemade snoots on the three LED lights
aimed at the smoke and a 65mm setting on my 24-105 lens which provided more DOF.
There is no question that to obtain superior smoke images, a strobe/flash unit is necessary, but...
my reason for these images, as Mike surmised, lie in a different direction rendering that strobe/flash unnecessary. Next time will do them in a totally darkened room.