Are there thermostat options available with hermetic sealing?

Yes, Honeywell's precision thermostat series (3000, 3100, 3100U, 3106, 3150, 3153, 3156, and 3200) are all hermetically sealed with steel housing and glass-to-metal seals at terminal junctions. These hermetic designs meet critical industrial and aerospace specifications for moisture resistance and environmental protection. (Pages 4-8)