Choosing the right size air compressor for a cleaning gun depends on several factors, primarily the air consumption requirements of the cleaning gun itself. Here are some general guidelines to consider:

1. Air Consumption of the Cleaning Gun: Check the specifications of your cleaning gun to find out its air consumption rate. This is typically measured in cubic feet per minute (CFM) or liters per minute (L/min). The compressor you choose should provide at least this amount of airflow to ensure proper operation.

2. Air Pressure Requirements: Ensure that the air compressor can supply the necessary pressure for your cleaning gun. Most cleaning guns operate effectively with a typical air pressure range of 60 to 90 psi (pounds per square inch).

3. Tank Size: While cleaning guns do not typically require a large tank size, having a small to medium-sized tank can help maintain consistent pressure and airflow, especially if you are using the cleaning gun intermittently.

4. Duty Cycle: Consider the duty cycle of the air compressor, which indicates the amount of time it can run continuously without overheating. For intermittent use with a cleaning gun, a compressor with a higher duty cycle (e.g., 50% or more) is preferable.

5. Portable vs. Stationary: Decide if you need a portable air compressor for mobility or if a stationary compressor will suffice for your cleaning tasks.

As a general rule of thumb, for most cleaning guns used in automotive detailing or household cleaning, a small to medium-sized portable air compressor with a tank size of around 20 to 30 gallons and a CFM rating matching or slightly exceeding the cleaning gun's requirements should be adequate. However, for industrial or heavy-duty applications, larger compressors with higher CFM ratings may be necessary.

Always refer to the manufacturer's specifications for both the cleaning gun and the air compressor to ensure compatibility and optimal performance. If you're unsure, consulting with a knowledgeable supplier or professional can help you determine the best air compressor size for your specific cleaning gun and intended applications.