Regulated mods, or those that have a micro-computer to allow variable voltage, have built-in protection and will shut the mod down in several circumstances. Protection against hard shorts from the battery, the atomizer, or the switch. Timed auto cutoff for the fire switch. On/off option. Mod cutoff for an over-drained battery. Limits on amperage draw.
A truly
mechanical mod has no electrical components. Only a mechanical firing button and direct battery connection to the atomizer connector.
Vent holes for release of gases from a venting battery should be present, as well as a
collapsable hot spring which attempts to slow down a failing battery about to go into thermal runaway.
The USER is the safety protection who must use smart & safe battery habits to recognize signs of an over stressed battery (heat from the mod, firing switch, or the battery, or a collapsed hot spring).
For the above reasons, a regulated mod is far safer for a new vapor to use until they have educated themselves in the ways of advanced vaping, understanding different battery chemistries and battery limits, knowing the basics of Ohm's Law, etc. For as simple as they are in construction, a mechanical mod represents more of a challenge to use safely.
A mechanical mod should always use a
Vape Safe Fuse.
IMR batteries are currently considered to be a safer battery to use over protected NCR/ICR batteries in both regulated and mechanical mods. A
Kick (a regulator drop in processor used on top of a battery) used in a mechanical mod not only turns it into a variable voltage mod, but also offers protective circuitry like the regulated mods have.
Below are links to important safety resources to assist novice vapors to learn the basics of battery and mod safety.
Vape Safe Mod Fuse
Mechanical Mod Proper Usage Guide
Battery Basics for Mods: IMR or Protected?
http://www.e-cigarette-forum.com/forum/ecf-library/129569-rechargeable-batteries.html
Images of failed mod batteries which have gone into thermal runaway