As others have advised, do a test, and the simple test described by trexx and Johns addendum works. I would only add to block up your enlarger lens and turn it on for 20 second or so so you are testing it for leaks and bounces from it at the same time. You can get many tests out of a single sheet, just save the short sheet in your box for the next testing time.
It is important to do the testing with papers you intend to use. If you bring a new paper into the darkroom test it. Some papers are fine under some kinds of "safe" light, and others are prone to problems with the same kind or intensity. You should test every so often anyway, but especially with a new set up or new paper.
The best reason to test is because most safe light problems aren't that apparent. You go on printing for a long time wondering why Goldfarb's highlights are so sublime compared to yours, because yours are missing just that little extra something, while you go through different developers, papers, films, toners, and all the other magic bullets, and the menacing secret was hanging over your shoulder the whole time.
That's the long way of saying a good printing regimen beats a magic bullet every time.
