One possible preliminary indicator of a "fire" about to break out in a church is smoke. (This is a secondary level, explanatory article in a series in which I am reflecting on building an imaginary "fire" detector for congregations. See this page for the original idea).
Smoke clouds people's ability to "see" and clogs breathing
In congregations, this potential-of-imminent-fire-warning smoke is most visible in negative or "dark" attitudes, in clouded dispositions, in scowling, unhappy facial expressions. It is whiffed and sniffed when a consistent pattern of negative talk is noticed, and that talk is most acridly about the pastor, other leadership, or the church itself. The talk mainly happens hidden away in semi-secret, though never secret enough to escape the nose or the imaginary fire alarm we are creating. There's a distinct feel and smell — an essence — to it, but the source may be hard to track. It is much like a stack of oily rags discarded in the corner of a garage that is warming up towards the internal combustion point where much to everyone's surprise it bursts into flame without a match.
Visitors might be the first to notice this pungency and remark "everyone seemed so tense" or "there was no sense of enthusiasm or playfulness" or "there were a lot of people huddled in small circles with their shoulders defensively hunched." These could be dangerous smoke signals. But of course, it's the rare visitor who will bother to give that direct feedback. Their not returning says something though. Yet the regular attendees do not often notice because they soon get accustomed to particular lingering smells.
Atmosphere that is clouded in this way also limits people's ability to breathe, to receive spiritual nurture and nourishment.
Good Smoke vs Not so Good
Smoke is not always a bad thing. In fact there are kinds of smoke-attitudes that are good. In the Bible, some even represent verification of God's presence. An atmosphere of excitement about what God is doing is good smoke. Incense is a kind of smoke — a positive fragrance. Positive smoke rises to God as a thank offering, an expression of gratitude (see Ex 30:8[and similar]; Lev 16:13; Rev 8:4; Luke 1:9-11; Rev 5:8 etc) and spirits are lifted by it or it is a sign spirits are lifting — your choice.
So Smoke is mainly about attitude and atmosphere
Smoke that indicates a fire is becoming likely is a symptom of unhappy attitudes. It can be a sign hearts might be hardening. It is rarely a good sign. A church that handles differences of opinion well does not produce smoke like this.
Attitudes need monitoring, as does atmosphere. A detector for real smoke checks the atmosphere for clarity at regular intervals, and if over a pre-determined set of them clarity is gone, it sounds an alert. We would do well to learn to 'watch' our own attitudes, to monitor our individual and collective tone in speaking, to alert and hold each other properly accountable for stinky attitudes that cloud the atmosphere. How that can be done specifically is for each context to decide. There are probably tools out there, but the technicalities of this are beyond the scope of this series.