A hand-held particle counter is a small, self-contained device that is easily transported and used, and designed for use with Indoor Air Quality (IAQ) investigations. Though lower flow rates of 0.1 ft³/min (0.2 m³/h) than larger portables with 1 ft³/m (2 m³/h), hand-helds are useful for most of the same applications. However longer sample times may be required when performing cleanroom certification and testing. (Hand-held counters are not recommended for cleanrooms). Most hand-held particle counters have direct mount isokinetic sampling probes. One may use a barbed probe on a short piece of sample tubing, but it is recommended that the length of the tubing not exceed 6 ft (1.8 m), due to loss of larger particles in the sample tubing.