There are lots of ways we use and apply this metaphor to our faith.
Many folks have been taken by the idea of the difference between deficit and asset models in working with people – the difference between thinking they are lacking or have deficits or have assets and something to contribute.
A fire extinguisher faith originally seemed to me to be a deficit model of faith. I have a problem, my faith is sitting in the corner of the room in case I have a crisis, so I go and get it, pick it up, use my faith to seek to solve the problem. We have fire extinguishers as a precaution , just in case , we carry on our normal lives, cooking etc
Historically, this way of drawing upon our faith has not been valued, we should be applying our faith to all aspects of our life, all of the time. But is this the only way to look at this?
Fire extinguishers need testing to check if they are working properly. Perhaps this is a valid reason why the metaphor of having a fire extinguisher faith is justifiable. That we know that our faith is there should there be an emergency and that we get it out on a regular basis, to check that it still works, and then when the fires happen, if they are accidental or arson, we can be secure that we have the resources to handle them. And also we know that some fires are so out of control, we call 999, 911 or the equivalent.