Subject: Can helium be mixed with hydrogen to form a non-explosive mix?

I've read that early airships often used such a mix.  Given that hydrogen costs 
about a third of helium, and is renewable, and that I am working on small scale 
airships, I am extremely interested in the answer to this question.  An earlier 
answer on this topic said essentially "Don't use hydrogen," but a technical 
answer is what I am seeking.

Re: Can helium be mixed with hydrogen to form a non-explosive mix?