The housing of our fanless machine is too hot to keep a hand on. Is that normal, or is the machine about to fail?

Usually it is normal. The housing of a fanless machine is its heatsink, and a hot housing means heat is being carried out as intended. A hand starts to feel uncomfortable at around 50–55 °C, while the CPU inside is designed to run up to roughly 100 °C before throttling. A housing at 55–65 °C in a 35 °C room under heavy CPU load is common. What matters is the internal temperature, not how it feels: 1. Read the CPU temperature in BIOS or with the vendor's monitoring software. If it sits near 100 °C and the frequency drops, the machine is thermally overloaded. 2. Check the clearance around the fins, the mounting orientation and dust between the channels. 3. Measure the air temperature around the machine and compare it with the datasheet range. Safety note: if operators can touch the machine, add a guard, because prolonged contact with a hot housing can cause minor burns.