By chance, I have a couple of holders from CCGS and CCCS, one for each company. These holders are similar in style, made of very thin clear plastic, and about the same size and appearance. In fact, both have semi-circular notches in the side to allow air into the holder. I believe these are the lower cost holder types and that each company offers a more rigid holder style as well.
Anyhow, I performed the Beilstein flame test with copper wire on both holders, and no green flame was observed after repeated attempts. So both holders appear to be "safe" from halide compounds.
