When sourcing a small air compressor, you must prioritize CFM (Cubic Feet per Minute) and PSI (Pounds per Square Inch) ratings. Ensure the CFM output is at least 1.5 times the requirement of your most demanding tool to prevent motor burnout. For durability, look for oil-free pumps if you require low maintenance and clean air, or oil-lubricated cast iron pumps for heavy-duty, continuous cycles. Additionally, verify the tank capacity (gallons/liters) to ensure it provides enough buffer for your specific usage scenario.