Stirling Engine Model Dont touch any part of the boiler and cylinder in heating process with your hands to avoid burns! After usage , make sure the spirit lamps are completely smothered and allow natural air cooling of the engine model. This model is not applicable to children under 4 years old. Children under 8 years old may use this model with presence of adults to avoid high temperature burns. Place the model in locations not accessible to children when not is is not usage. When adding alcohol ,the spirit lamps must be smothered.