My commercial oven cooks unevenly and takes longer — is it the door gasket or the calibration?

Short answer: uneven, slow cooking on a commercial oven is usually one of two things — a worn/torn DOOR GASKET leaking heat (so the oven fights to hold temperature and hot/cold spots appear near the leak) or the THERMOSTAT being out of CALIBRATION (so the dial says one thing and the cavity is really another). You can check the gasket yourself; calibration needs a probe thermometer to confirm and a tech to correct. Start with the door seal — it's the cheap, common one.

How to tell which: - Door gasket (check this first): inspect the seal all the way round — torn, hardened, flattened or missing sections let heat escape. Tell-tales: heat/steam escaping around the door, the area near a gasket gap cooks worse, the oven struggles to reach or hold temp. Do the paper test — close the door on a slip of paper at several points; if it pulls out easily, the seal's gone there. A worn gasket is a cheap, quick replacement. - Calibration: if the gasket's sound but food still cooks as if the temperature's wrong, put an oven-safe probe thermometer in the cavity and compare to the set point. A consistent offset (set 200°C, reads 180°C) = out of calibration, which a technician recalibrates/adjusts (and on some ovens it drifts over time). - Also rule out: a failing element/burner or a dead fan in a convection oven (no fan = uneven, because it's the fan that evens out the heat).

Order of attack: gasket → thermometer check → tech. The gasket is the most common and cheapest, and a leaking one both cooks unevenly and wastes energy holding temperature.

For a busy line this is a consistency-and-cost issue, so don't limp it — a commercial kitchen-equipment technician can replace the gasket and recalibrate in one visit. F&B folks — gasket or calibration more often for you?