Knowing how to handle any given situation can mean the difference between perfect results and paying for it. I face this issue everyday.
Take a look at the photo below. When I was asked to work on this car, I didn't think I would see something like that. My guess, about 20 years of dirt.
This was behind both seats of a 1988 Mazda RX-7. I detailed this car during the summer of 2017. Personally maintained before that. I don't recall if it was ever professionally detailed. Almost a 20 year old car, a classic at this point.
Keeping in mind that this car was 20 years old as I detailed it, drove home the fact that I need to be careful. Cars and parts on cars deteriorate over time. For example, you never know what plastic piece is so dried up and brittle that you brush over it with your vacuum hose and it breaks. Or it snaps off its post like a radio knob.
In this case with the carpet, I can't tell how good of shape the backing is. Water damage could have broken down the backing. As soon as I start scrubbing it with a brush, the brush will start pulling the fibers out.
Ruining the carpet is never an option. By the way, I looked it up. If I ruined the carpet, a replacement would have been between $150-$300. Not terribly expense to replace though. Once you start getting into cars this age replacing parts with aftermarket parts can devalue the overall value of the car. Not an option.
Well. Being careful, using gentle tools and products...the results speak for themselves. Quality products, proper techniques and experience winagain.