There are some important considerations when choosing a portable weld fume collector. First, airflow: Generally you need 900 to 1500 CFM for a small, portable unit to be an effective ventilation tool for welding operations. Second, filtration: There are a few critical elements to consider here. Make sure you have a spark arresting first stage. This helps to safely remove sparks or embers that might find their way into the air stream. Also make sure you have an inexpensive pre-filtration stage to protect your primary filter. Finally, make sure you have at least MERV 15 filtration efficiency. This will ensure safe removal of hexavalent chromium from work areas. Finally, some units offer HEPA filtration for additional safety. Other units offer carbon as an option to control odor. This is a nice feature if odor is at all of concern.