Can't answer that, there's all kind of humidifiers, but probably not unless it's designed to be IN a reptile cage. Might not be safe for the snake, for one reason or another. Can you post pics or a link to the actual product?
Also- how are you covering up the screen? With what, specifically? How big are the air gaps you're leaving, exactly? Pics would also help. You might just be doing that incorrectly, as many do.
Also, how are you measuring the humidity? (I ask, because the inexpensive & ubiquitous humidity gauges are not very accurate.)
What would be an accurate method of measuring humidity?