About as safe as Russian Roulette.

It is true there is a recommended method for heating infused oils, the idea being that heating drives off the water which provides an attractive harbor for botulism spores. However, it's still a low-acid environment and the recommendation is that the heat-infused garlic oil should be refrigerated and kept no longer than a month. It certainly isn't canned.

This approved method was developed by Ellie Topp, a Canadian home economist and microbiologist. The brochure below provides specifics.

Carol

Here is a link that might be useful: Flavoured Oils Brochure

There are some pretty scary stories, for sure ! I hear all sorts of crazy things.
Here we tell people store garlic only 2 weeks in the fridge, then throw out. Of course, if it shows any signs of spoilage before then, throw it out. It doesn't look, smell, or taste bad to have botulism in it, either. You can't see, taste, or smell botulism.
Wow, in a sealed jar, in oil, with the absence of air ! Bottled botulism...

This is copied and pasted. The link is at the bottom:
STORING GARLIC IN OIL
Extreme care must be taken when preparing flavored oils with garlic or when storing garlic in oil. Peeled garlic cloves may be submerged in oil and stored in the freezer for several months. Do not store garlic in oil at room temperature. Garlic-in-oil mixtures stored at room temperature provide perfect conditions for producing botulism toxin (low acidity, no free oxygen in the oil, and warm temperatures). The same hazard exists for roasted garlic stored in oil. At least three outbreaks of botulism associated with garlic-in-oil mixtures have been reported in North America.

By law, commercially prepared garlic in oil has been prepared using strict guidelines and must contain citric or phosphoric acid to increase the acidity. Unfortunately, there is no easy or reliable method to acidify garlic in the home. Acidifying garlic in vinegar is a lengthy and highly variable process; a whole clove of garlic covered with vinegar can take from 3 days to more than 1 week to sufficiently acidify. As an alternative, properly dried garlic cloves may be safely added to flavor oils.

Here is a link that might be useful: UC Davis on storing garlic.

I have been intrigued by the possibility of this as well. I have a dehydrator. So acording to the website provided above, by lina lou, I could dehydrate my garlic and then put it in oil. Would it then be safe to leave at room temp, and if so for how long? Just curious!

Thanks, bluejean in ohio

Does the danger diminish if I cook the garlic and then try to infuse it? Is it only garlic? If I make a pesto base,leaving the garlic out and freeze it to be spooned from the freezer and melted before each use, is that OK?

I love putting food by, but I have to admit, I'm a chicken and I want to rely on those visual indicators ( the depressed seal)to keep me safe.

Maybe that is why I havent tried salmon or other meat yet.

Below I've provided a link to an Oregon State Extension document on herbs and vegetables in oil that will clarify some of your questions regarding any differences between fresh and dried products.

Cooked garlic still poses risks. Remember, cooked garlic is just as low-acid and some water will remain, so the risk of botulism is still there.

Regarding your other question, you can freeze pesto base, with or without garlic, or freeze the completed pesto, including the cheese and nuts, thaw (in the fridge) and use as fresh. Freezing does not present any risks. Canning does.

Some people prefer to blend just basil and oil because it's more versatile and freeze as cubes. Others do either a pesto base or completed pesto. Some feel it tastes better if cheese and/or nuts are added at the time of use, but others don't perceive any difference and would rather make the complete recipe and freeze. As a frozen product, you can add garlic and freeze with no safety concerns.

Carol

Here is a link that might be useful: Herbs and Vegetables in Oil

It is all fresh foods that pose a risk. Cooking won't help at all, as mentioned in the section I posted above.
Still, must be stored in the fridge at all times and thrown away within 2 weeks. Some safety experts say 10 days.
This is what Colorado State says:
Even when dried, there is still the potential for risk, unless the vegetable has been acidified to a pH of 4.6 or lower.

You can freeze it fine and take out what you want and eat in a few days.