The rotobrush is the best ductcleaning machine on the market. I personally own two. It is not just a shop vac, it actually has a rotating brush on the end of the hose which is changable depending what construction of duct work you are cleaning. it is also available with a video camera so you can see what you are doing and also show the customer what you are doing. it actually works to clean the duct work unlike others i have owned or used.
Except for a very few circumstances, duct cleaning is quite possibly the single most useless thing a person can have done to their system.
The stand alone Rotobrush machine is little more than a glorified shop vac with a spinning brush on the end of it. Not enough suction to do the job, and the brush becomes useless once it gets past the branch duct and into a trunk line or duct that is larger than the brush.
Duct cleaners love it because it can be a high profit margin item.
Unfortunately for the homeowner it does nothing to reduce airborne particles, allergens, dust, or improve system performance.
The one or 2 studies that made it look like there were some minimal positive results included cleaning out the indoor unit and installing a high efficiency filter.
the rotobrush is junk i used it for a company for 5 years if you are in a two story house good luck tryiny to get it done the vent to the first floor.the brushes blow more of the dust away from the vacum then it sucks up.your better off getting a negative air machine like the abatement hepa-aire unit used with a compressor to blow stuff down to it i have used both and the abatement machine does a way better job.some people will say that it does brush the walls clean.but either does the rotobrush when you try to put it in a vent it won't go done.they make attachments to hook to compressors to make it a air whip that cleaned the duct walls just fine.plus if you got the rotobrush stuck in a wall with the brush rapped around a wire good luck getting it out.trust me go with a negative air setup with compressor.it will do a way better job
to do a good job with the rotobrush and for it to work right you have to know how to use it. i use one and it works great. also i hear people saying they have problems in flex with it. again, have to know how to use it. i've never had a problem in flex.
I personally do not really like it . I think it is a glorified shop vac. You can't get some of the big things you find in people's ducts out with it and the rotobrush cannot go as far as you need it sometimes. It just does not seem that it does as thorough of a cleaning as our regular vacuum system.
If your machine is broken and you need it in a tight pinch it can be alright but I would definitely not recommend it.
If used properly I've been able to do a DECENT job with one. You need to use the correct brushes and take your time. Works pretty well in round lines, in trunk lines you need the bigger brushes, reversing its direction will move it from one side to the other. The machine needs clean bags and air filters to keep a decent suction. I've been able to take my time with a rotobrush (g/f's parents house) and do as good as a job as more expensive methods but it takes a long time. Baseboard mounted supplies can be damn near impossible so be wary WHERE you are using it before quoting customer prices. Mini cameras are a requirement for checking your work and looking for missed spots.
After all that, if a customer ask me about duct cleaning I recommend calling a specialist in that field. It just takes too long too do a good job, so you either make a profit and do a crappy job or you dont make a profit and do a good job and I dont have time for either of those options.