In 2008, EPA established a National Ambient Air Quality Standards (NAAQS) for airborne lead of 0.15 micrograms per cubic meter (mcg/m^3), to become effective in, I believe, 2016. That standard is directed at the lead-processing industry and so specifies that an operation must emit a reasonably large amount of lead to fall under the regulation. I don't think even a very large indoor range would come close to that limit. Under our regulatory system, the individual states are free to enact regulations that are more stringent than the national standards, but I'm not aware of any that have done so, which of course is not the same thing as saying that there are none.
To the best of my knowledge, there are no environmental regulations that apply specifically to ventilation of indoor shooting ranges. OSHA standards, which apply only to employees, and then only to companies over a certain number of employees (I forget exactly, but it's something like 10 employees), specify that no employee shall be exposed to airborne lead concentrations in excess of 50 mcg/m^3, averaged over an 8-hour period, but doesn't specify how you need to ventilate to achieve that standard.
There are, however, many sources available on-line that talk about how to ventilate a range properly and I'm sure you can Google them up. The NRA has long recommended minimum velocity of air flow down range, i.e., away from the shooting line, of 1 foot per second and you can easily calculate the require minimum cfs necessary to achieve that for a particular range. That would truly be a minimum, however, because uniform laminar air flow across the shooting line is a near impossibility.
For what it's worth, I can honestly say that I've never shot in an indoor range that I thought was sufficiently ventilated, and that includes the near state-of-the-art ranges at the Smith & Wesson training facility in Springfield, Massachusetts. I've had issues with elevated blood lead levels over the years, and now wear a half-face respirator with P100 filters whenever I shoot indoors; my lead levels are now back within the "normal" range. I consider the respirator to be every bit as important a part of my personal protective equipment as my eye and ear protection.