Why is it said that humans emit infrared radiation, or are these included in it.

https://hps.org/publicinformation/ate/q1617.html

Hi Vivi,
I think you're a bit confused by the two common uses of radiation. The article you put the link to deals with radioactive materials and particles.

Infra-red (IR) is part of the electromagnetic radiation spectrum, as are some of the rays mentioned in the HPS article such as x-rays. Humans put out as we make excess heat most of the time and this comes out at wavelengths longer than the red end of the spectrum. We can't see IR but we can feel it. Our eyes are just the wrong sort of detector to see it without the help of instruments.

"Hope is a duty from which palaeontologists are exempt."
David Quammen