The Gillian® 3500 & 5000 are industry leaders in back-pressure performance, reliability and ease-of-use. These pumps offer flow rates up to 3500 & 5000 cc/min respectively. And thanks to several advanced features, these pumps overcome the main causes of sampling errors – saving you time and money. The air flow display holds calibration for 30 days, even with atmospheric changes. While Gillian air sampling pumps are known for their strength, the back-pressure capabilities of the Gillian 5000 are the highest in the industry for any personal sampling pump.