Far infrared is also known as thermal radiation. It is less harmful to the human body than red light and blue light. If you are under a cloudy sky and it is hot, say 30 degrees, that is how harmful thermal radiation is to the body.
The hight you climb up the electromagnetic spectrum, from radio waves to thermal waves to light waves to UV Xrays and Gamma rays, the more they can interfere with atoms and molecules, because they can disrupt bonds, ionize, and so forth.
So IR can only heat the body and can't ionize or disrupt the body.
Far infrared is the heat you feel when you are far away from a fire and the heat travels towards you without air transport. Near infrared is the heat you feel closer to the radiator, and that which causes convection nearest to the heat source, it gets absorbed faster by the air.
Insulation is most important for heating, as more than 50 percent of heating is lost through the ceiling. modern buildings in the west have high roof insulation standards.
oil heaters tend to absorb near infrared and reflect it back as far infrared better.
I think that the smaller and hotter the source, the nearer thermal wavs it produces, and the larger and less hot surfaces can make more far infrared.
It sounds like a lot of marketing terms.
Oil heaters are traditionally very efficient. I had one which i bought a bit rusty for 15 euros and it has lasted 5 years. the only issue with oil heaters is that they can eventually leak when very worn or less strongly welded.
microwaves are less HF than thermal, and they have not been associated with any health risks either even from phones used all day beside the ear.
You can think of far infrared as the warmth that is reflected from a hot wall heated by the sun. It is one of the least dangerous forms of radiation.
you may consider investing in a HPS lamp of 600 or 1000w because it produces 90 percent heat from that, and also vast amounts of light which are good for mental biology and good for growing tomatos and strawberries in the middle of winter. because they go in a ventilated area under a table in the house, the also radiate well. of all kinds of radiators, i prefer by far sitting under a hot lamp with a summer hat tending plants in the middle of winter, it's definitely hot. A 600W lamp can produce about 200 tomatos, 100 strawberries and 20 peppers and some melons/beans etc, in the winter months.