Electronic – When can free-floating electrical contacts become dangerous (e.g., start a fire)

In general, when should free-floating electrical contacts be considered potentially dangerous? Danger may be direct (e.g., due to electrical shock) or indirect (e.g., due to fire risk).

In this question on SE.SuperUser, a poster asks if it's safe to have two wires for a power switch exposed in their household. Their concern seemed to focus on electrical shock to a person or pet.

The dangers of electrical shock to humans is discussed in these questions:

• "How much voltage is “dangerous”?"

• "Safe current limit for human contact?"

This YouTube video claims that 12V can start a fire:

Can 12 volts start a fire? Yes! Wake up people. Every day I hear people say "oh it's only 12v it can't do much". Shock wise, you're safe. Fire wise, treat it like line voltage, do it right, and safely. Because this can happen in your car, or even a charger. Electricity is electricity. It causes heat, and under the right condition, a fire…
Keep this in mind with your car audio installation too! Do it right, and make sure it's fuse protected!!

–"Can 12 volts start a fire?", YouTube

Presumably, we can construct hypothetical scenarios in which extremely tiny voltages or currents can trigger an unstable system. This question intends to focus on realistically possible scenarios that could accidentally happen in everyday environments, e.g. in households.

Question: In general, when should free-floating electrical contacts be considered potentially dangerous? Danger may be direct (e.g., due to electrical shock) or indirect (e.g., due to fire risk).

Alternative statement: Bob has an open circuit with two exposed contacts on his bedroom floor, built into into clothing (as part of some prototype wearable device he's working on), or in closet, pantry, desk drawer, or some other messy location where he/someone-else/misc.-items may come into contact with the electrodes. The power source behind the electrodes maintains a potential difference of \$v\$ between them, up to a maximum current of \$i_{\text{max}}\$. As a reasonably educated electrical engineer, Bob understands the potential danger of coming into contact with these electrodes. Over the domain of voltages/current-limits \$\left(v,~i_{\text{max}}\right)\$, in what regions would Bob be:

• unconcerned with any potential danger;

• mildly concerned with potential danger;

• worried;

• reasonably certain something bad'll come of it?

Clarifications

Something is "dangerous" if any of the following apply:

1. Any person or pet coming into contact with the free-floating electrical contacts might suffer physical pain or/and any type of observable physical harm.

2. It's potentially possible for the electrical contacts to cause any sort of common household item to catch fire when exposed to the electrical contacts at length.

3. The electrical contacts could foreseeably cause observable damage to common household items, the house itself, etc..

As for risks:

1. I'm primarily looking for heuristics. The goal is to separate "reasonable safety concerns" from "absurdly paranoid concerns".

2. Contrived risks may be omitted. This is, I'm sure that we can come up with hypothetical scenarios, e.g. where the electrical contacts trigger a measuring device that intentionally starts a fire; however, I'm concerned with risks that might be accidentally encountered.

3. Risk-qualification's going to be fuzzy, and that's okay. Perfectly valid answers may declare there to be a grey zones in which the presence-or-absence of danger is unclear/fuzzy.

The electrical contacts may be qualified by:

1. Being either AC or DC current.

2. Having any constant voltage between them.

3. Having any current-limit.

An ideal answer might provide a heuristic that a normal person could use to assess how they should feel about the potential danger from two exposed electrical contacts randomly scattered in their home of a known voltage-difference with a known current-limit for both AC and DC.