As with all things scientific and industrial, there are ways to quantify just how good steam is and where it can be used. We can think of these as three basic grades of steam: Utility, Culinary, and Pure. These essentially deal with how sterile the steam has to be, how much or how little water vapor it can carry, and what contaminants or additives it can be exposed to.
There are numerous applications where the chemical make up of the steam isn’t a terribly big deal. Consider steam used for heating oil pipes. It doesn’t matter if the steam is wet or dry, if it contains any anti-corrosives, or if we put anti-freeze in it to prevent pipe bursts in the return lines. This is steam that’s never going to come into contact with humans, never touch food or clothes, or otherwise be an exposure risk. We put up a nice biohazard sign, some skulls and crossbones on the pipes, a sign that reads “if you drink, touch, or breath this, not only will you die, but it will be slow and painful,” and everything is pretty much set.
The same can be said for steam used exclusively used to heat a building or dedicated to other purposes. In these environments, there’s not going to be human exposure, so it’s treated like any other chemical. In these instances, it’s helpful to use additives to extend the life of the equipment.
Wet steam can be destructive to valves, turbines, and other moving equipment. To combat this, we can add chemicals to the water vapor in the steam. Typically these are anti-corrosives, but anything that water vapor will carry is a viable material. It all depends on the job at hand.
Some jobs require stricter regulation. Steam that will come into contact with cooking equipment or food needs to be more thoroughly regulated. Culinary Steam generally comes from a dedicated boiler/steam system that is kept to a cleaner standard. This includes filtration to remove solid contaminants, strict regulation of what additives, if any can be used, and even possible FDA inspection and testing.
Steam like this is often used to heat food and food equipment in massive kitchens. Food manufacturers don’t use normal kitchens. It’s not practical to use even 10 quart pots when you’re making millions of quarts of soup in weeks. What is effective, is massive tanks big enough to pass for extra deep hot tubs. These can be open air tanks or pressure vessels to pressure cook food. The same process control technology used in chemical plants and elsewhere allows for incredibly fast, precise, and repeatable food production. In the soup example, whole rows of tanks can be fed and pressurized with steam from a central boiler, rapidly cooking the food inside.
This extends to other technologies too. There are steam powered ovens. From a scientific basis, an oven is just a convection cooker, we heat the air which then heats the food. It’s a little inefficient and risks drying out whatever we’re cooking, but it’s also a little slow. At industrial scales, we can add steam to the oven. The hot, moisture-rich steam can moisten food and provide heat more quickly. It also works without any individual heating elements, which can improve efficiency, given we’re never waiting for an element to heat up or having to stop to replace one.
Despite the name, this steam grade may also be used in other settings. Science labs and certain areas of manufacturing may also use so-called culinary steam. This is for a wide range of reasons. In the lab, there needs to be as little contamination as possible and there are workers around to get exposed. In manufacturing, there may be concerns of delayed exposure. If you use steam to melt plastic for a kids toy, it would be a very bad idea to add lead to the steam.
Culinary steam isn’t always clean enough. Sometimes there needs to be completely pure, clean steam. This is typically dry steam, given that is pure steam with no vapor content at all. Science labs with specific contamination concerns and areas of manufacturing needing extreme heat or extreme heat control would use pure steam.
That’s not to say pure steam is necessarily always clean. There needs to be the maintenance, filtration, and cleaning to keep it clean even after it’s been generated. In this sense, dry steam is not necessarily always a pure-steam. It can become contaminated by airborne particles. Pure steam involves a commitment to thoroughly maintaining the plumbing and generation system.
The idea behind this steam is to provide a heat source that won’t impact what’s being heated. Even a bunsen burner can contaminate certain tests with unburned particulates. Pure steam however, won’t contaminate the specimen anywhere near as readily. At the same time, pure steam is ideal for sanitary work, cleaning food vessels, cleaning clothes, and so on. The temperatures available effectively incinerate bacteria and viruses without the use of open flames.