Most gas power stations generate steam using the exhaust from their gas turbines to generate extra electricity.

Cracks and crevices in the ground allow air in. Not very much air - the coal is just barely alight, just barely smouldering, like charcoal and a barbeque.

Normally, coal would go out with so little air. However, it's trapped deep underground and the heat can't escape. So, even just smouldering, with the heat being trapped, will keep the fire alight.

Immunotherapy is a new type of drug technology. The drugs are new with a ton of nasty and unexpected side effects.

Doctors technically can prescribe any drug for any reason. However, they usually prefer to only prescribe drugs where the drug has had a clinical trial to show that the drug works in that situation. Similarly, the FDA won't approve a drug for use in a particular situation, unless there is a clinical trial showing that the drug is safe and effective in that situation.

The problem is getting clinical trials done. If a drug is brand new, with a ton of side effects and quite likely many unknown serious side effects, who is going to volunteer for a trial. Not just that, but is it ethical for a doctor to do a trial on a pore tally dangerous treatment, if there is already something which works.

When it comes to new drugs, the first clinical trials to be done tend to be done in situations where there is nothing else available. In this case, it is ethical to get volunteers for the new treatment, as the only alternative is no treatment.

Most of the clinical trials for immunotherapy fall into this category, although as doctors get more experience, and the drugs are better understood, there are some clinical trials looking at earlier use being prepared or are underway.