Depends on how it's stored. In a well sealed air tight container it'll last pretty much indefinitely. If it's not well sealed, it'll absorb moisture and smells from its surroundings, which will make it both icky and ineffective as a raising agent, but it probably won't kill ya!
Once a can is opened, fresh baking powder should be good for 3 to 6 months.
6-12 months
How long does harry hornes custard powder last when can is opened
Generally baking powder will last for six months to one year.
ever.
For a good long time if it is kept properly stored. Here is a test you can use to make sure your baking powder is usable . Put water in a teaspoon and sprinkle a little bit of the baking powder in the water. If your baking powder is good the water will fizz sort of like a soda does. if you don't hear or see the fizz then baking powder is no good and should be tossed out.
As long as its not made with powder sugar. Are you baking a cake?
No
Only substitute baking soda for baking powder if the cookie dough will be baked within 30 minutes of mixing. Baking soda begins to lose potency as soon as it gets wet so baking powder is used when the dough will be allowed to sit for a long time before baking.
Baking soda is not hazardous. Infact let it on ur skin for how ever you please.
Scotch that has been opened will last indefinitely if kept in a cool dark place.
About a week.
Honey is a shelf-stable product, opened or not. It will last indefinitely as long as the honey hasn't been contaminated.
It doesn't take any time: instantaneous!