If you have an area that is “classified” as a confined space, then that is probably because someone has already evaluated its possibilities for ventilation and determined that there is insufficient “natural ventilation”.
To answer your question very simply: Yes, you need to provide positive outside air flow and exhaust of whatever fumes and gases build up in the room. (It doesn’t do any good to, say, position a fan in a doorway if it’s the only doorway. That doesn’t add much air inside the room; it just helps to move around what’s already there.
As long as it is a “confined space” then you also need to take other measures, such as:
– training the people who will work there in “confined spaces working requirements” and having a written policy for working in confined spaces;
– continuously monitoring air quality inside with approved oxygen level monitors;
– posting at least one person outside the space to monitor those inside, who can call for immediate help (probably from people with self-contained breathing apparatus) in case anyone inside is overcome. (It doesn’t do any good for a single person outside to attempt a rescue on his own and to be overcome himself; that just adds to a death toll.)
You don’t really need to measure “volume flow rate”, I don’t think. You need to assure that the oxygen level doesn’t drop below about 20%, that noxious / flammable gases don’t accumulate to dangerous levels, and that people know the dangers of working there and have “exit and rescue” plans.