This is what happens when you in-breath a little too strongly and the venturi effect of the regulator kicks in, it's like a blast, the regulator is delivering a huge quantity of air... actually the rest of the time I was breathing very lightly to avoid it... very unpleasant I have to admit... Understandable why this balanced single stage regulator didn't get the commercial success he was expected to have... I will post a whole article about this reg on my blog soon, stay tuned! Thanks, cheers!