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who we are

PSI was founded in 2014 to provide field verification, engineering peer reviews and consulting services to the cannabis extraction industry. We have extensive experience spanning across the nuclear, chemical, pharmaceutical and oil & gas industries. 

Our cannabis engineering consultants have more than 170 combined years of industrial experience and have performed more than 3,600 extraction-related consultations. Currently operating in 50 US states and 5 countries, we are proud to offer the fastest and most rigorous third-party engineering reviews in the cannabis extraction industry.

Years Combined Experience

Chris Witherell, PE

Chief Executive Officer

Chris has more than 30 years of experience in equipment design engineering, design verification, project engineering, and engineering management using ASME NQA-1 quality programs for commercial nuclear power and Department of Energy clients. He is a founding partner of Pressure Safety Inspectors, LLC. Chris has a Bachelor of Science in engineering with a mechanical specialty from the Colorado School of Mines. He is a licensed Professional Engineer in Arizona, California, Colorado, Connecticut, the District of Columbia, Florida, Georgia, Hawaii, Iowa, Maine, Massachusetts, Minnesota, Michigan, Mississippi, Montana, Nebraska, New Hampshire, Nevada, Ohio, Oregon, Rhode Island, South Dakota, Utah, Washington, and Wyoming.

John R. Andrzejczak, PE

Founding Partner

John has more than 40 years of experience engineering custom research and process equipment for the chemical, petrochemical, nuclear, and pharmaceutical industries. John’s Process Safety Management (PSM) experience includes facilitating and scribing Process Hazard Analyses using HAZOP, and developing PSM systems for process plants and Safety Analysis Reports for nuclear facilities. As quality assurance manager, he wrote, implemented, and maintained ASME Boiler and Pressure Vessel and ASME NQA-1 quality assurance programs. He is a licensed Professional Engineer in Alabama, Alaska, Arkansas, California, Colorado, Delaware,
Idaho, Illinois, Indiana, Kansas, Kentucky, Louisianna, Maryland, Missouri, New
Jersey, New Mexico, New York, North Carolina, North Dakota, Pennsylvania,
Oklahoma, South Carolina, Tennessee, Texas, Vermont, Virginia, Washington, West
Virginia, and Wisconsin.

“Crazy fast response and Field Verifications. This is an insanely huge step for our company and it’s all thanks to you.
Can’t wait to use your services again in the future!”

Zachary Hexamer, Flora-California