Vacuum pumps are used to 'suck' air from suitable sealed vessels and chambers creating a near vacuum.
Several types are available through lab suppliers and all have pros and cons. When choosing to buy a vacuum pump, one of the main things to consider is how often will it be used and for what purpose.
Large heavy electric pumps work very effectively, vacating a large bell jar in seconds. They are however sometimes noisy, expensive and need regular maintenance. Hand-held vacuum pumps are cheaper but often need a strong hand to operate. They are a lot more portable than the larger electric pumps.
Most lab suppliers offer both types, some sell a variety of electric pumps which vary in terms of price and amount of air they pump in a fixed amount of time. When selecting an electric pump, be aware that some are quieter than others. A loud pump is not very useful if you are trying to vacate the air from the bell in a bell jar equipment as the noise created by the pump may be louder than the bell!
Also be aware that some of the more heavy-duty electric pumps are very heavy. Information regarding the pump's loudness and weight may be listed in supply catalogues or can be obtained by contacting the suppliers directly.
Some electric pumps may need oil adding to a chamber within them on a regular basis. Ensure you select the correct type of oil and do not overfill. Filling details should be supplied with the pump or can be obtained through suppliers.