#1: What is the application?
There are MANY different types of vacuum pumps and not all pumps can be used in the same industries. This is why it’s important to understand your ultimate needs when it comes to purchasing a vacuum pump. Different applications call for different types of equipment. before you purchase your vacuum pump, make sure the amount of power you need for your task is attainable and that it can handle all types of samples that you will be processing. Research and be aware of what kind of pump you will need!
#2: What is the required operating 
vacuum?
Make sure you have a clear understanding of the operating vacuum of the vacuum pump needed for your application. Every operator should understand the difference between operating vacuum and the ultimate vacuum. The operating vacuum is the vacuum required for a specific process, while the ultimate vacuum is the deepest vacuum at which a pump can operate.
#3: Is contamination a risk?
Since a vacuum pump pulls the process towards the system, it’s important to take into consideration how wet or dry your application is. Knowing what application you are using for your vacuum pump will ensure the correct protection process for the front of the vacuum pump is considered.
#4: Can I use a dry vacuum pump?
Although there are a lot of oil-based wet vacuum pumps out in the market, oil-free or dry pumps are lower maintenance which makes your job easier. Dry vacuum pumps are efficient but noisier than traditional vacuum pumps.
#5: Think long term! What is the lifetime cost of a vacuum pump?
Lap equipment is expensive and it's best if you get a high-quality pump. It’s important to consider the lifetime cost of a vacuum pump. This includes the original purchase price, maintenance, repair, and pump protections. Your cost might seem pricier in the beginning, but you’ll be saving money in the long haul. Think long term and get a high-quality vacuum pump!
#6: Explosion-Proof Hazardous Environment?
Are there explosive/flammable gases in the area where the pump will be used? If so, an explosion-proof pump is mandatory.
#7: Oxygen Pumping?
Will the pump be required to pump high concentrations of oxygen? If so, a pump with regular hydrocarbon-based pump oil will not work. Hydrocarbon, when combined with oxygen will explode. You will need a pump specially-built w/ PFPE / synthetic fluid.