Extensive toxicity evaluations have been compiled by nationally recognized US Medical laboratories & institutions on Halon 1301 and 1211. These evaluations have shown that Halon 1301 is the safest extinguishing agent available, and that Halon 1211 is the second safest.
Dual Halon concentrations of about 5% by volume in air are adequate to extinguish fires of most combustible materials. This concentration is equivalent to emptying twelve (12) 2.5 lb units in a closed room of 1000 cubic feet, which would be highly unlikely.
Halon 1211 extinguishers should not be less than 2½ pounds capacity. These extinguishers should have a minimum 5 B:C rating; not less than 8 seconds effective discharge time; not less than a 10 foot range..."