Safety notice

Read before you build. Reboot · 50 Machines is an educational work about how historical and appropriate-technology machines work and go together. The guides simplify. They are not engineering drawings, are not certified, and do not replace training, local regulations or the supervision of a qualified professional.

Several machines involve pressure, extreme heat, mains electricity, toxic or flammable gases and corrosive substances, and can cause serious injury, fire, explosion or death. If you build anything, you do so at your own risk, in line with the law that applies to you (electrical installations, pressure equipment, gas, waste, radio emissions), with protective equipment, and never let children do it unsupervised. Nothing in this notice limits your rights under consumer law.

Specific warnings

• Boilers, rocket-stove boiler, steam engine, Icyball: pressure vessels can explode. Always fit a correctly rated safety valve; never heat a sealed vessel without one. The Icyball uses ammonia, which is toxic: outdoors only. Pressure equipment is regulated (in Spain, Royal Decree 809/2021).
• Wood-gas generator and biogas digester: carbon monoxide is odourless and deadly; hydrogen and methane are flammable. Outdoors only, with a CO detector; never in a garage or closed room.
• Arc welder: mains voltage and the arc can kill and blind. Use a welding mask (shade 10–13), gloves and flame-resistant clothing. Any connection to the mains must be made by a licensed electrician.
• Salt-water chlorinator: produces chlorine and hydrogen: toxic and explosive. Ventilate; never mix with acids or ammonia. Wrong dosing does not make water safe to drink.
• Lead-acid battery and acids: sulphuric acid burns, lead is toxic. Goggles and gloves; always add acid to water, never water to acid. Dispose of as hazardous waste.
• Spark-gap transmitter: high voltage, and broadband radio emissions are illegal without a licence (in Spain, Law 11/2022 on telecommunications). Only as a shielded demonstration or into a dummy load.
• Kilns, forge, foundry, glass and lime kilns: temperatures above 900 °C, molten metal, zinc and lead fumes and caustic quicklime. Never let moisture reach a mould or crucible; wear full protective equipment.
• Dams, water wheels, towers: moving water and falling loads kill. Check local permits; never work under a raised load or in flowing water alone.

Last updated: 13/10/2026