Jud and I have raised all of our greens in relatively low humidity as far as tropicals go (probably avg. around 65%), with no respiratory problems whatsoever. This is not to say that a humidity as low as 50% wouldn't be a problem however. If you have an internal cage heat source, you can easily lower the humidity down to 50% if you are not careful, and I would then agree with your friend that this could be a problem. I feel that if it is maintained at least above 60%, there shouldn't be a concern. I think that with greens, stress is more of an issue with health problems than anything else. If I were to guess, I would assume that your friend was working with wild caught imports which are obviously going to be under a large degree of stress and therefore more susceptible to RI. The additional condition of a very low humidity would definitely add to the stress of a wild caught snake. I would be curious as to the source (cb or wc) of these snakes, and how long they were in captivity before they showed symptoms of RI. Thanks,
Kelly