Thank you @Pied_Pfeffer, @Jboy, @Tropical_Willie, @snowberry for your answers. I didn’t know there is an expiration date on the side of the fire extinguisher. I will take a look. I have two extinguishers. One has a gauge, one does not. They are more than 10 years old, and the one with the gauge still shows the needle in the green, so I figure the gauge must be useless and misleading. A property manager told me that you have to shake these things every 2 or 3 months or so, so that the powder doesn’t settle to the bottom and clog up the works when you need the extinguisher the most. He said that most people either don’t know this or forget to do this. However, it would seem to me that if the powder is heavy enough to settle to the bottom, it would have done so after just a few days. How inconvenient to have to shake it every few days just to keep it in good working order! So that can’t be the whole story. So, thank you, @Pied_Pfeffer, for the link. I will take a look at the article!