FWIW, I always use a blowoff tube at this point, at least until the active portion of fermentation is done. It no more difficult than putting an airlock on and you just never know when you'll need a blowoff tube or not.
You can never go wrong with a blowoff tube, but it also depends on what you're fermenting in, the yeast strain, how much headspace, and the yeast strain. Better to err on the side of caution if unsure.