Simulates between 10,500 and 29,000 feet. I do not have the mask, I would advise bringing a mask to test that it is producing roughly the correct pressure deficit. I don't want to sell you a dud and this hasn't been used since my uncle stuck it in his closet several years ago. Probably any cheap gas mask or single filter respirator could be jerryrigged to test it. A vac gauge sensitive enough might work.
Also disclaimer for this type of equipment: This thing can simulate Everest. If you have heart or breathing problems misusing this can be the end. I would measure what kind of vacuum it's drawing and compare this to what it's supposed to read before you use it during serious exercise.
Cautions aside it's a powerful tool to amplify your performance.