The quenching rate constants of CH(A (2) Delta and B (2) Sigma(-)) by Ar, O-2, CS2, alcohol, and halomethane molecules have been measured at 290 K by using the direct time-resolved technique. The electronically excited CH radicals were produced by laser photolysis of CHBr3 at 266 nm and the time-resolved emissions of CH(A (2) Delta and B (2) Sigma(-) -X (II)-I-2) were then monitored as a function of time using a fast digital storage oscilloscope coupled with a microcomputer. for a given partner, the collisional removal rate of CH(B (2) Sigma(-)) is faster than that of CH(A (2) Delta) except for O-2