Forget the oil... You cannot install your generator or your pump in an unheated attic! No portion of this equipment, including the water supply line and the steam output line, should be installed in an unheated space where it may freeze.
This will most certainly do great harm to your equipment and possibly even your home. If you think about it, this is a just a specialized water heater. You wouldn't install your water heater in an unheated attic, would you? Of course not.
To answer your questions:
- pure Eucalyptol freezes at 30.2° Fahrenheit
- AromaMist oils do not contain alcohol or any other smell enhancement additives
Most commercially distributed oil blends for steam rooms contain ISO PRO Alcohol or similar inexpensive additives to enhance their aroma. These types of chemicals only imitate the aromas and can have a harsh, unnatural smell. AromaMist Essential Oils contain no smell enhancement additives, only the essence of the oil itself.