You need a power scraper with a vacuum for that type of job, something like this http://paintshaver.com/
As long as the client was happy and we were complying with regulation, we used the cheapest tools possible. You could spend spend 1000 or whatever it costs on this thing that vacuumes up paint and put the job in the red or you could spend 10 bucks on some paint scrapers and get shit done in the same amount of time. These kinds of tools also don't always work or take a lot of overhead to set up which is lost money in wages as well as time on the job that could be spend painting the house. The difference between 50% profit and a loss is surprisingly thin.
For a house with a huge amount of lead paint this kind of tool might be useful but that job would be quoted differently and likely would go to a specialist that charges more accordingly and maybe even contracts someone else to do the actual painting. These days most houses that need it have been done.
Ideally, you would reuse the vacuum for other jobs in the future.
It did not work well. Everything had to be just right for it to work properly. If the paint was not a uniform thickness, if there were any old paint drips hanging over the edge of the siding, or if the siding was not laid straight the same width across the wall, it wouldn't shave off the paint evenly.
We found the best tool for the job was a radiant heat gun made from an old toaster oven and a paint scraper. You'd heat the paint until it started to soften, then scrape it off with a putty knife.
Like the parent said, it was difficult work requiring at a minimum a ventilator and gloves, and try the best we could, it was impossible to contain all the paint chips. But I think a few paint dust chips left behind is probably trivial compared to the amount of lead in the soil around our house from decades of cars and trucks going by our home burning leaded gasoline.