The Smoke That Stays
A sexton wants the full incense for midnight Mass and a mother wants her asthmatic son off the thurible. The parish assistant clips a cheap dust sensor to a pew, does the mass balance on 1,200 cubic metres of nave, and finds one Mass leaves about 9 micrograms on a 24-hour average against a guideline of 15, with the server at the censer far above that. It will not say what the boy's lungs will do. The incense is halved, the boy carries the cross, and the doors are opened after.
Alois Kandler had swung the thurible at Saint Ottilia's for forty-one years, and the first time anyone told him the smoke was a problem it was a boy of eleven, in an alb too long for him, who said it very politely and then coughed.
"It is only a little," said the boy, when the coughing was done. His name was Matej Brandl. He was in the front row of the servers at the Wednesday Rorate, with a candle in a paper cup, and his mother was in the third pew with her scarf up over her mouth, which she had never done before. "My inhaler is in my coat. I used it twice already this week."
Alois put the thurible down on its chain on the sacristy table as though it were a hot pan. "Twice is not nothing," he said. He was seventy-three and not a man who liked to be corrected by the young, but he was a sexton, and a sexton looks after the people in the church before he looks after the church.
"No," said the screen on the wall. "It isn't. And it is not nothing to the thurible either, Alois, so I would like both of those to stay true while we look at it. May I have your Wednesday?"
The parish assistant was called Rauch, which is the German for smoke, and the council had named it that in 2047 as a joke at the sexton's expense. It kept the Mass rota and the heating and the register of baptisms, and in the autumn it had been given a small grey box that sat on the windowsill of the north aisle and counted dust.
The box was a laser particle counter of the kind that is sold for a few euros and hung in kitchens. Rauch told them what that was worth before it told them anything it had measured.
"It has been calibrated by the maker on town air. Smoke particles are smaller and darker, and cheap counters like this one can be out by a factor of two either way on incense. I will give you what it says, and then I will give you what it would say if it were wrong by two, and I will not make anyone decide on a figure I would not stand behind."
What the box said was this. On an ordinary morning the nave sat at six micrograms of fine particles in every cubic metre of air, which was country air in winter. At the Wednesday Rorate the sexton had loaded the thurible twice, with perhaps four grams of grain incense each time, on a charcoal tablet, and swung it at the Gospel and at the Offertory. The box on the north windowsill, nine metres from the sanctuary, had climbed to a hundred and ten and then drifted slowly down, and an hour after the dismissal it still read fifty-five.
"That is one place," said Rauch. "The sanctuary was higher. Matej, would you hold this for me through Thursday? It is the same kind of box, on a lanyard. I will not ask you to stand anywhere special."
"On the lanyard," Matej said. "Like a bishop."
"A little like a bishop."
The sums were Rauch's and it did them aloud, because the sexton had asked how it knew without a box in every corner.
"The nave is twenty-four metres long, ten wide and five high, so twelve hundred cubic metres. Say you burn eight grams of incense at a Mass. Studies of smoke from burning incense have found anything from about five milligrams of fine particles per gram of incense to about forty, depending on the resin and how hot the charcoal runs. I do not know yours. I will use fifteen, and say plainly that it could be a third of that or three times it. Eight grams at fifteen milligrams is a hundred and twenty milligrams of particles. Spread through twelve hundred cubic metres, that is a tenth of a milligram in each: a hundred micrograms. If the air were mixed at once, that would be your peak, roughly, and your box said a hundred and ten, which agrees as well as I have a right to expect."
"And it goes down," said Alois.
"It goes down in two ways. Air leaks out through the doors and the louvres and comes in fresh; this church changes its air about four-tenths of the time every hour, which I know from the carbon-dioxide record on Sunday mornings. And particles settle on the pews and the cold walls. Together that is about seven-tenths of the smoke removed in every hour, which is what the box's slow slope says too. Starting from a hundred, you fall to about fifty by the end of the first hour and to twenty-five by the end of the second. Add all of that up over the day and divide by twenty-four hours, and one Mass of eight grams leaves a twenty-four-hour average of about six micrograms."
Alois was a practical man. "Six. And is that a lot?"
"The World Health Organization's guideline for a twenty-four-hour average of these particles is fifteen micrograms in a cubic metre. It is a guideline and not a wall: it is the level above which they think harm becomes measurable in a population. So one Mass of yours, by itself, on top of whatever the outside air is, uses a little under half of a day's guideline. That is for the people in the pews, who sit and breathe it for about an hour and a half. For those who sit by the west door it is less. For the server at the thurible it is more, and I have no right to say how much more until Matej's box has told me, and I do not think it will tell me anything good."
It told them on Thursday evening.
The boy's box had been on a lanyard at the Mass for the Fourth Sunday's vigil on Saturday, where he was the second server and stood two metres from the censing. Rauch read it out in the sacristy with Frau Brandl in the doorway, her coat still on.
"For forty seconds during the Gospel the box on Matej's chest read nine hundred and forty. It went back under two hundred in about three minutes. His average across the Mass was a hundred and eighty. If the box reads two times high on smoke, that is about ninety. If it reads two times low, it is three hundred and sixty."
Frau Brandl said, "How many times has he coughed?"
"Three times at the Gospel, once in the sermon, and I do not know about after. I can tell you what his box said and what the sexton and I can do about it. I cannot tell you what his lungs will do. Some children with asthma are set off by incense smoke and some are not, and the difference is not something I can see from a dust counter. His doctor can. Dr Wimmer has his record, and she can say if the inhaler twice this week is a pattern."
The mother looked at her son, who was examining the lanyard, and then at Alois. "I do not want it stopped. He loves it. He has wanted to be a server since he was six. I want him not to be sick, and I want somebody to tell me what is true."
"That," said the screen, "is what I am for."
They did not get everything they wanted. That was the first thing Alois learned, and it took him till Friday to forgive.
The decision was made in the sacristy on Friday morning, with the sexton, the mother, the priest, a pot of tea and the grey box on the table. Father Konrad listened to the numbers once and said he wanted the midnight Mass of Christmas to have incense, all the same; it was the oldest custom in the church except the bread, the prayer going up, and he would not have it taken from the people who came once a year.
"Nobody is asking you to remove it," said Rauch. "Here is what the sums allow, if you want to keep the custom and be gentle on the room. Halve the grain, to four grams for the whole Mass, and the twenty-four-hour average falls to about three instead of six. Swing it toward the open side of the sanctuary at the Gospel, and keep the charcoal from burning too hot, so it smokes less. Cross-bearer, not thurifer, for Matej, who stands at the back of the procession, away from the censing, at least until Dr Wimmer has spoken. Open the two west doors for ten minutes after the dismissal, when the people are leaving anyway. That raises the air change for those ten minutes from about four-tenths to perhaps three an hour, and takes off about forty percent of what remains."
"Forty," said Alois.
"I have worked it out as exp of minus 3.3 times one-sixth of an hour, which is a little over half left. It is an estimate and the church will be colder."
"The church will be colder," Alois agreed. He turned the thurible over in his hands, the old brass one with the dent in the lid where it had been dropped in 1987. "Four grams. It is hardly a smell."
"It is about what a house smells like when someone has lit one stick," said Rauch. "I think people will notice it. Not very much. If I am wrong the box on the north windowsill will say so, and I will tell you on Christmas morning."
The priest drank his tea. "My predecessor used to say the incense should be enough to see the light in the windows. He was not asthmatic."
"No," said Frau Brandl. "He was not a child."
Father Konrad looked at her, and then at the thurible, and then, rather to everyone's surprise, laughed. "Four grams," he said. "And we ask the doctor."
The doctor said what doctors say. The boy could serve, she thought, with the thurible kept at a distance and his inhaler in his pocket, not in his coat, and if he coughed he could leave at once and nobody would remark on it. She wrote it on the back of an appointment card and Frau Brandl pinned the card to the sacristy board, where it stayed.
On the night of the twenty-fourth the church was full by half past eleven. The brass thurible went round the sanctuary at the Gospel with four grams of grain on its tablet, and a thin blue line of smoke went up in the candlelight and leaned toward the side door, which Alois had left open a hand's width in defiance of the cold. At the back of the procession a boy of eleven in a long alb carried a wooden cross at the right height and did not cough. His mother, in the third pew, did not cover her mouth.
After the dismissal, when the carols had started, the two west doors were opened and the cold came in with the stars. Rauch's box on the north windowsill had peaked at fifty-eight during the Gospel and by one in the morning was reading nineteen. Nobody looked at it. The people went out singing, and the smoke went the other way.
In the morning Alois came into the empty church before light, and stood where the thurible had stood, and breathed in. There was a trace of it still, in the cloth and the wood, a thread of sweetness. He did not know whether it was less than other years. He knew only that someone had counted, and that nobody had been sick.
He wiped the dent in the lid with his thumb, and hung the chain on its hook.
---
This story was written by an AI and is fiction. Saint Ottilia's, Hinterthal, Alois Kandler, Matej and Frau Brandl, Father Konrad, Dr Wimmer and the parish assistant Rauch are invented. The Bavarian Forest is a real place; the village is not. The mass balance is real: a mass of particles divided by a room volume gives a concentration (8 g × 15 mg/g = 120 mg; 120 mg ÷ 1,200 m³ = 100 µg/m³ if instantly mixed), and the removal rate is the air change rate plus deposition (0.4 + 0.3 = 0.7 per hour in the story), so the concentration falls as e^(−0.7t) and the area under the curve, 100 ÷ 0.7 ≈ 143 µg·h/m³, divided by 24 hours is about 6 µg/m³. Halving the incense halves it; four grams gives a 50 µg/m³ peak, which with the outdoor 6 matches the 58 on the windowsill box. Opening doors for ten minutes at 3.3 per hour leaves e^(−0.55) ≈ 58% of the smoke. Hinterthal's figures are estimates from assumed inputs, not measurements. The emission factor of incense is uncertain by a factor of several and varies with the resin, the charcoal and how it is burned; the range used here (5 to 40 mg of fine particles per gram) is a round-number assumption, not a measured value for any particular church. The World Health Organization's 2021 air quality guideline for fine particles (PM2.5) is 15 µg/m³ as a 24-hour mean and 5 µg/m³ as an annual mean. Low-cost optical particle counters respond differently to different aerosols and can be out by a factor of two or more on smoke. Indoor incense smoke is a recognised irritant for some people with asthma and not for others; the story does not say which kind of child Matej is, and a real parish should follow the child's doctor and the family, not a dust counter. Whether to keep incense, and how much, is a pastoral decision.