We sometimes use an inexpensive vacuum sealer here at our offices. I was curious about the pressures involved, and whether these could be used as an alternative to expensive vacuum pumps in the science lab. We put a partially inflated balloon in the sealer and ran it. The pressure reduction is modest, to about 0.4 atmosphere. At the end of the movie, we released a valve on the sealer to let the air back in.
The bottom line is that these devices might be useful for some science lab activities, but they do not produce very low pressure. On the other hand, the device works well for some applications, demonstrating what happens to objects containing air when the air pressure changes. Some students who have noticed puffed up bags of chips on airplanes or when visiting the mountains may find this interesting. The results of our experiment including a movie is included in the Logger Pro file.