One possible preliminary indicator of a a fire about to break out is a lack of Oxygen.
Something is displacing the oxygen, maybe Carbon mon-or-di-oxide, or the oxygen is being consumed. So, basically it is oxygen depletion.
In congregations, the equivalent of oxygen depletion is spiritual starvation. Spiritual oxygen is nurturing and sustaining and purifying spiritual good from God, When fire is developing, oxygen gets used up quickly, and other toxic vapours replace it. In churches toxic attitudes and thoughts displace maturity and purity and contaminate healthy breathing. People lose the ability to think clearly.
This is a clear sign a real fire is about to break out, especially if there is also smoke and heat.