There are a lot of vacuum cleaners with HEPA filters these days, but finding a good one can be difficult.  The purpose of the HEPA filter is only to trap emissions from exhausting though the vacuum cleaner.  Finding a vacuum that is effective enough to remove the dirt from the nap of the carpet and home furnishings is most important.  If you vacuum fails to remove the embedded dirt that the HEPA filter will serve little value.  A two motor vacuum with a power nozzle is highly recommended to accomplish this task.  Once you find a two motor vacuum that is effective, you should then look and see if it has a HEPA filter.  This way you will remove all the embedded dirt and have clean emissions, which is optimal for a clean home. 

According to the definition in 40 CFR 745.83:

"HEPA vacuum means a vacuum cleaner which has been designed with a high-efficiency particulate air (HEPA) filter as the last filtration stage.  A HEPA filter is a filter that is capable of capturing particles of 0.3 microns with 99.97% efficiency. The vacuum cleaner must be designed so that all the air drawn into the machine is expelled through the HEPA filter with none of the air leaking past it."

Therefore, renovation firms should look for a vacuum cleaner that was designed to be operated with a HEPA filter, rather than a shop vacuum that can be fitted with a HEPA filter in place of the original basic filter.  A vacuum retrofitted with a HEPA filter is not necessarily properly sealed or designed so that all of the intake air goes through the HEPA filter.  EPA also recommends that renovation firms ask the manufacturer or retailer whether the machine has been tested to ensure that it achieves the high efficiency required of a HEPA filter (capturing 99.97% of 0.3 micron particles).