Measure room air and representative growing material separately. Active mycelium releases heat, so the centre of a bag or bed may differ from the wall thermometer. Record the measurement location, crop stage and time before comparing readings.
Temperature requirements vary by species, strain and growth stage. Oyster is a group of species; there is no universal 30-degree death threshold for all oyster mycelium. Use the supplier or institutional protocol for the actual strain and distinguish air targets from substrate limits.