About Us

About Us

Tetra Heating and Air Conditioning’s journey started in 1968 out of the trunk of a 1962 Ford Falcon and went by the name of Sentinel Refrigeration headed by Mike Donnelly. In 1971 we became a C-38 specialty contractor and in 1995 added C-20 when Kent Donnelly took ownership. In 2011 we changed our name to Tetra Mechanical still installing high performance, safe, comfortable and efficient air comfort packages for families and businesses.

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What we do

Air Conditioning Services In Simi Valley, CA

Air Conditioning

If something isn’t installed correctly, it won’t work as it should. This is especially true of air conditioning (HVAC) equipment. So, it’s important to make sure your local HVAC service technician is experienced, trained, qualified, and backs their work.

Heating Services In Simi Valley, CA


Don’t stay uncomfortable this winter! A central gas heating system should be able to provide a consistent amount of warmth to keep you comfortable inside your home. A great furnace can give the best balance of comfort, cost-efficiency, and atmosphere for your home.

Indoor Air Quality In Simi Valley, CA

Indoor Air Quality

Your home’s indoor air quality matters for the safety of your home, your family’s quality of health, and energy cost-savings. Learn more on the importance of the right affordable systems available. Get your home tested and begin breathing easier today!

Service In Simi Valley, CA


Breakdowns are a headache, you want to have someone with knowledge responding to your service emergency. Improperly diagnosed units, improperly repaired units can cost you hundreds if not thousands of dollars over time with wasted energy, premature failures.