Mycelium is the network of fine threads through which the cultivated fungus grows in its substrate. Visible white growth is useful to observe, but a white surface alone does not prove uniform colonisation or freedom from contamination.
Spawn run is the colonisation stage. Its duration and environmental requirements depend on the species, strain, substrate and method. The fungus respires and releases heat: a closed cultivation bag does not mean the room needs no ventilation. Follow the validated bag design and incubation protocol, and monitor representative substrate and air conditions.