HERE IT IS

>So lets say we have a scalpel, right? Simplest medical device there is. There's a number of ways to make it totally(ish) sterile- gases, steam, dry heat, gamma radiation.

>But as you ask- the little bacterial corpses are still there. Waiting, one presumes, for tiny necromancers.

>The problem occurs when you stab someone with the scalpel, preferably in a medicinal way. The bodies immune system works by identifying certain chemical triggers in bacteria, and has no way to know that, for example, the lipopolysaccharide hanging around in someone's heart is not part of a bunch of living bacteria, but the floating corpses of dead bacteria.

>The dead byproducts of bacteria are called "pyrogens" because they cause (among other things, such as death) fevers.

>Where do they go? Nowhere. Bacteria are small enough that water has completely different properties on their level. Beyond rinsing off gross matter and reducing bacterial load, washing can't do much.

>So for things like heart surgery scalpels, there will usually be a second step of "Depyrogenation" This is the process, not of killing bacteria, but of removing the bits left behind so they don't trigger an immune reaction. This varies widely in complexity depending on what you have to depyrogenate- steel scalpels are easier than an injectable drug, for example. Typically, the goal of the process is to so thoroughly break down the biological material left behind.

>**Are my hands covered in bits of dead bacteria?**

>No your hands aren't covered in dead bits of bacteria. They're covered in happy, healthy bacteria.

>**Then why wash my hands??**

>Washing your hands removes dirt and debris that carry the nastiest bacteria. Sterilizing your hands is a ridiculous notion however- your hands are made of cells, bacteria are made of cells. Anything that would kill them would kill your cells. Your hands, and literally everything else on the world not currently under direct gamma radiation bombardment, are covered in bacteria,

>Quick run down on terms:

>"Cleaning" a medical device is basically doing dishes-getting blood n bits off the reusable ones. (plz dont reuse single use medical devices that makes regulatory professionals sad 😭)

>"Disinfecting" is using chemicals to get something purty darn clean.

>"Sterilization" is killing all* the germs on something

>"Depyrogenate" is taking bacterial corpses and reducing their remaining structure to a point where your immune system won't recognize it and freak out.

>*SALx10-6 is the typical sterility level for a medical device. one in a million germs/one in a million devices.