Like almost every Brazilian, I cook with this pressure cooker very often. The things you have to be aware is the relief valve and the safety seal.

The relief valve, on top of the pan, should be clean and move freely. That’s where the pressure will gradually escape from the cooker while you’re cooking.

The safety seal is a rubber that melts if the pressure is too high and then relief the pressure very fast. Make sure this seal is alright.

Another thing I do and recommend is to never fill the cooker with water past the middle of the cooker! You must have an empty space to build pressure! If you put too much water, the pressure will increase really fast and blow everything up. So take care about the amount of water you put and never exceed the middle of the cooker

This is not really an issue. Check a few things: Is the seal under the lid still in good condition? Does the pop-it emergency pressure release still move? Is the pressure tube that the weight fits on clear and unclogged? Is there a pressure gauge?

The seal, pop-it, weight and gauge for almost any model can be bought on Amazon or eBay for less than $15 as a set. So as long as the body is in good condition you can replace every other part for almost nothing compared to buying a new canner. An older gauge can be tested and calibrated at your local extension office.

Is the body in good shape? No dings, dents, warped bottom? Do not buy a cooker with any of these problems.

All the canners at second hand markets made it to the second hand market after being used and they didn’t explode.

It takes a ridiculous amount of effort to try and explode one old made in the last 60 years. Find the make and model. That will tell you when it was made and if there was a recall.

Stick with the name brands, Mirro, Presto, All-American.

I’ve included a lot of things to check for here to avoid this issue but I want to stress that it is almost impossible to blow up a pressure canner. I have four of them. I have followed canning groups for a long long time. I’ve seen exactly one explosion and that was because someone tried to open a canner with a failed lid lock before the pressure dropped. This resulted in the contents of the jars suddenly expanding and hitting the ceiling. Not the canner exploding, it was the food in the jars. And that was easily avoidable by just waiting.

I own four pressure canners. Only one was bought new. The rest were from yard sales and thrift stores. I’m not happy with the deals on the Mirros but they still do the job. I have no issues buying used cookers or canners.

I avoid all electric ones. Not for safety but lifespan. The electronics will fail. The more feature that have the faster they will fail. They have incredibly limited capacity. When they fail they are trash. You can’t repair them. A manual canner will last you a lifetime and if any part of than the body fails you can replace it for cheap.

Side note, All-American doesn’t have a seal. So you can ignore that.ake sure the screws move nicely. Be happy you found an extra expensive canner that will last forever.

Bonus material: canners and cookers are different. You can cook in a canner but can’t can in a cooker.

Bonus bonus: If you get an aluminum bodied canner and you use it for canning instead of cooking, you will start to see a thin black patina develop on the inside. Do not try to clean that out. It’s aluminum oxide, fine layer of sapphire that will protect the canner from the inside. The darkness is your friend.

test the valve when you start to cook. if the button doesn’t release air and the valve indicator isn’t moving, turn off the heat and move the pot off the stove right at the start. in that case let it cool down for a long time before opening it, so even if there’s still preasure, no hot contents get ejected.

They will have some kind of pressure relief valve, to let steam out and prevent an explosion. They only become dangerous if that valve isn’t working (assuming that whatever keeps the lid on is intact and still strong).

Look for damage around the seal between the pot and the lid, and look for damage to the clamp or latch which holds the lid down against that seal.

Then look at the valve. It’ll probably be a heavy object (such as a lump of metal) which sits on top of a hole of some sort, or it could possibly be something spring loaded. Either way, check that it moves freely.

After that the only additional thing you could do is a pressure test, where you basically deliberately overpressurise it and see if it explodes, but if you had the means to do that safely then you wouldn’t be asking for advice here so I don’t recommend it.

There is essentially zero risk of a pressure cooker exploding. If pressure starts to build without being released due to a malfunction, the seals are going to fail before the metal container will. Yes, it would be a mess, but it’s something you can deal with. It’s not going to detonate and kill people.

If you are in the US, check with your local government office and/or university. In Wisconsin, the university has extension offices and you can take your pressure cooker in to get it tested. They will tell you if it is safe, and if not what you need to do to make it safe. They do this as a free public service

Make sure the seals are good and the vent is clean. I’m used to indian pressure cookers where the weight is removable. I’d recommend buying a replacement safety valve. They’re pretty cheap

All of these, plus don’t over-fill when cooking, since you want to make sure you keep any food from obstructing the pressure release while it’s going

I’d just buy an Instant Pot.

Put it inside another pressure cooker

Replace any gaskets expansion plugs etc. make sure it’s in good working order air flows through the vent at the top.