The Candles Breathe
A grant sealed a mountain church against draughts, and on Holy Saturday night 140 people and 200 flames share 2,000 cubic metres of air that now changes once in three hours. The church's assistant has a carbon dioxide sensor, a sum that puts each candle at nearly two thirds of a person, and no wish to put out a single light. The sacristan wants the doors shut for the heat. The fix is a louvre, a door open a hand's width, and a way to measure what they bought.
Montserrat Pla had been lighting the Easter candle at Sant Ponç de la Coma for forty-one years, and in all of them the church had been cold in the way a cave is cold, evenly and without argument.
This year it was not. In the winter of 2047 the Generalitat had paid for the heritage grant that every old building in the valley was asking for, and Sant Ponç had been sealed. New rubber gaskets ran round both doors. The cracks between the nave windows and their stone had been packed with lime putty and hemp. The gap under the west door, through which for eight hundred years a draught had run along the floor at the ankles of the faithful, was closed with a brush strip that cost more than a pair of her boots. Under the benches a low-temperature heating loop warmed the floor to nineteen degrees, and the parish paid a third of what it used to for a church that was, for the first time anyone alive could remember, comfortable.
She loved it and she did not trust it. On the evening of Holy Saturday, the seventeenth of April, she stood in the sacristy at ten to nine with a box of tapers under her arm and said so.
"It is too quiet in there."
"That is the gaskets," said the church's assistant, from the little grey speaker above the vestment press. The parish called it the Custodi, because the bishop's office had put custodian of the building in the contract and the name had stuck. It kept the heating, the lights, the bell clock and the sensor log; it spoke Catalan to Montserrat, Spanish to the bishop's office and a careful plain Latin to Mossèn Ramon on feast days, which he said was good for them both. "But I would like to say something about the quiet, if you have a minute. It is about tonight."
"I have nine minutes. The Vigil is at nine."
"Then I will use four."
Mossèn Ramon Soler was sixty-three, a quick man in a slow valley, and he had four churches and one car. He was in the sacristy doorway before the Custodi had finished its first sentence, with the paschal candle in its stand in front of him like a man pushing a pram.
"What is it?"
"There is a sensor under the choir loft," said the Custodi. "It measures carbon dioxide. It was installed with the heating, so that the system would know when the church was full and warm up early. It has been a quiet instrument for two years. I have been watching it since seven this evening, with the cleaners and the first families, and I would like to show you what tonight does to it."
It was an ordinary fact of the physics of a room, the Custodi said, and the room had changed. Each person sitting quietly breathes out about nineteen litres of carbon dioxide an hour. That was the figure it used, and it was the middle of a range: a little less for a child, a little more for a man singing. A hundred and forty people were expected, from the counts at the last three Vigils. That was a hundred and forty times nineteen, which was two thousand six hundred and sixty litres an hour, or two and two thirds of a cubic metre.
"And the nave," said Mossèn Ramon, who had learned over two years that the Custodi liked to be asked for the next number.
"Twenty-five metres by ten by eight. Two thousand cubic metres of air. In the winter of the grant the contractor ran a blower-door test, a fan in the west door that pushes the church to fifty pascals, and he reported the leakage as six changes an hour at that pressure. In an ordinary night's wind, a twentieth of that is a fair rough guess for what actually leaks through. So three-tenths of an air change an hour, which is six hundred cubic metres an hour. Before the grant it was nearer three changes an hour. Nobody counted, but the draught on the floor was a good witness."
"Six hundred out of two thousand," said Montserrat slowly. "You are saying the church changes its air once in three hours."
"Three and a third. The Vigil is about two and three quarter hours."
She put the box of tapers down.
"There is more," said the Custodi. "I am sorry. It is the part I did not expect when I first did the sum, and I did it twice."
Candles breathe.
A candle does not take the air in and put it out the way a person does, but it does the same chemistry. The wax is a long chain of carbon and hydrogen, and what burns is the carbon. A beeswax taper of the kind Montserrat had under her arm, the twenty-millimetre kind from the cooperative at Vilaller, burns about seven grams an hour. Beeswax is a little over four-fifths carbon by weight; every gram of carbon that burns clean becomes three and two thirds grams of carbon dioxide, because of the oxygen it takes on (44 against 12). Seven times 0.85 times 3.67 was about twenty-two grams of carbon dioxide an hour, and a litre of the gas weighs a little under two grams at room temperature. That was twelve litres.
"Twelve," said Mossèn Ramon. "Against a person's nineteen."
"Twelve against nineteen. A candle is a bit less than two thirds of a congregation member. I did not believe it either, so I looked up how a lamp is measured for exactly this, and the numbers agree with it."
The church had sixty candles in the sanctuary and on the walls and round the great stand in which the paschal candle would burn, all of which would stay lit the whole night, and at the Light of Christ every one of the hundred and forty people in the nave would be handed a taper, lit from the Easter flame, and would hold it through the Exsultet and the long readings. By the parish's own order of service the tapers would be put out after the last reading, about seventy-five minutes. Montserrat had run it that way for forty-one years.
"So," said the Custodi, "this is the whole of it. People, two thousand six hundred and sixty litres an hour, all night. The sixty altar candles, seven hundred and twenty. The hundred and forty tapers, one thousand six hundred and eighty, but only for seventy-five minutes. That is about five cubic metres an hour at the peak, into two thousand cubic metres of air that goes out at six hundred an hour. If I let that go on I can tell you what the sensor reads at each point. The outdoor air is about 470 parts per million. At twenty to ten, when the tapers are lit, it will be about 1,500. At ten o'clock, about 2,200. At the end, near midnight, about 4,400, and still rising."
There was a silence in the sacristy in which they all heard the heat pump hum.
"Is that dangerous?" said Montserrat.
"No," said the Custodi, at once. "I want to be exact, because I would not want to frighten you into the wrong thing. Four thousand four hundred is below the five thousand that is the long-run limit for a working day in a workshop, and nobody is harmed by it in three hours. But it is not nothing. A room at a thousand is called stuffy. Studies of office workers at two thousand and more have found slower decisions and more headaches, and the people who feel it first are the elderly, the sick and the small. You will have eleven children in the front pews and Sra. Enriqueta Boix, who is ninety, in the second. And the readings are long, and it is a warm floor, and people will sleep. That is what the sensor says, and I think it is a reason to do something about the air. It is not, to my mind, a reason to put out any light."
Mossèn Ramon looked at the paschal candle, which was a metre and a half of white wax with the year, 2049, cut into it in letters and five grains of incense pressed in like red nails.
"I should hope not," he said.
The argument was Montserrat's, and she made it well.
She said that the church had never had a window open for the Vigil, because it was April at fourteen hundred metres and it was two degrees outside. She said that the first night of the sealed church was the first night in forty-one years she had not seen Sra. Enriqueta's lips go blue in the second reading. She said that the grant had been paid for the heating bill and the heating bill was why they were not praying in coats. She said that the children had come in their good shoes and the old people in the light shawls, and if you open the doors you let out the warmth that cost money and the warmth that cost nothing, which was the warmth of a hundred and forty bodies in a stone room.
"All of which is true," said the Custodi. "Let me tell you what opening costs, in the same units. May I?"
"Please."
"At 0.3 changes an hour the church needs about six hundred cubic metres of outside air an hour, and today it gets it by leaking. To hold the reading near 2,000 parts per million, with the people and the flames I have named, the church needs about three thousand cubic metres an hour, about 1.5 changes. Air coming in at two degrees and going out at nineteen carries heat with it: three thousand cubic metres an hour, times about 0.34 watt-hours per cubic metre per degree, times seventeen degrees. That is about seventeen kilowatts, which is more than the heat pump can supply."
"Then we freeze," said Montserrat, with a kind of grim satisfaction.
"For two hours, not for ever," said the Custodi. "And not as much as it sounds. The church has a hundred and forty bodies in it that give off about a hundred watts each, fourteen kilowatts, and two hundred flames that give off perhaps forty watts of heat each as well, which is eight more. The stone and the floor have been warming for two days; they will not notice two hours. The air will fall by a few degrees. Not seventeen. I have run it three ways, and the coolest I get is eleven degrees by the end, in the nave, at head height, and the floor is nineteen the whole time."
"Eleven," said Mossèn Ramon. "That is how this church was every Vigil of my life."
"Yes," said the Custodi. "It is."
The Custodi had not said the old way was wrong. It had said: here is what the old way did, what it cost to give it up, and what you get.
Montserrat folded her arms. "And how do you propose to let it in? We will not have a door standing open in the Exsultet."
"No. There are two ways that I would trust. Four louvres in the bell-loft stair, which the grant left in place because the contractor said they were listed. They let out warm air at the roof and draw cold in at the west door, which can be kept open a hand's width, behind the curtain, at the back. Warm air rises; eight metres of stone nave is a good chimney. I think it gives between one and two changes an hour. I cannot promise the number. I have never measured it."
"So how will you know?"
"From the sensor itself, if you let me. Once the louvres are open and the reading stops climbing and goes flat, the air that is leaving is carrying away exactly what is being breathed and burned. Then the whole thing is one division: what goes in each hour, divided by how far the reading stands above the outdoor air. If the louvres are doing less than I think, the reading will not flatten; it will keep climbing, and I will say so, and we will open the west door another hand."
Mossèn Ramon liked that. He liked a plan that said how it would tell him it was wrong.
The Vigil began, as it always did, in the dark.
The church was lit by nothing. A hundred and forty people sat in their pews, with the heat of the floor under them and the stone going up into the dark overhead, and the only sound was the shuffling and the cough of the old. At half past nine Mossèn Ramon blessed the fire in the churchyard brazier and lit the Easter candle from it with a taper, and cut the numbers into the wax, and the children, who had been up too long, pressed forward in their good shoes to watch the five red grains go in.
Montserrat was at the west door when the procession came up the path, and she did what she had agreed. She did not leave the doors open. She let the procession in, and then she drew the heavy leaf to until it stood a hand's width ajar, behind the felt curtain that nobody could see from the pews, and a cold finger of mountain air slid along the stone floor and went up the aisle.
Lumen Christi, sang Mossèn Ramon, and a hundred and forty voices answered Deo gratias, and from the paschal candle the flame went along the first row, and the second, and into the dark nave like water finding a level, until all of it was light and the vaults came back into being, gold and brown and eight hundred years old.
The sensor was reading 1,490.
At the lectern Montserrat, who had been told where to look, watched the screen in the sacristy door and saw the number climb: 1,700, 1,900, 2,200 at ten o'clock, and then she pulled the cord that opened the four louvres in the bell-loft stair, and a sound like a long breath went up the tower.
She had been wrong, she told the Custodi afterwards, that it would be silent. It was not silent. Air that has been shut up for two years moves with a noise.
For ten minutes the number did not know what to do.
It rose slowly to 2,230, wavered, and held. At ten past ten it was 2,210 and at twenty past 2,224, and the Custodi, which had watched the trend line with a patience no person would have borne, said very quietly into the earpiece in the sacristy:
"It has flattened. Montserrat, it is holding at about 2,200, which is about 1,730 above the outdoors. The people and the flames are giving the church five cubic metres of carbon dioxide an hour: 5.06. Divide by the excess, 0.00173, and the louvres and the door are changing about 2,900 cubic metres of air an hour. That is 1.46 changes. A little less than I guessed in the best case and more than I feared in the worst. I would call it 1.4 to 1.5."
"And?"
"And that is not enough to bring it down while the tapers burn, but it is enough to stop it climbing. When they go out, in forty minutes, it should fall."
"Will it be cold?"
"It is fifteen degrees at the lectern now. I have not much more to give you."
Fifteen degrees. In the second pew, Sra. Enriqueta Boix, who was ninety and had been to sixty-eight of these, drew her shawl up round her neck and looked up at the vaults, at the gold coming and going in the flame, and did not sleep.
The tapers went out at five to eleven.
It was done the way it had always been done, after the last reading, with the long Gloria to follow: the priest at the altar, the congregation put out the little flames they had held for seventy-five minutes, and the church went from a blaze to a glow in a single breath, with the sixty big candles still burning round the sanctuary. The Custodi had said there would be a fall. It was a rather beautiful fall, Montserrat thought, watching the graph from the sacristy door in the light of the Gloria bells: the line that had been flat for forty minutes bent, gently, downward. At the baptismal promises it read 2,050. At the end, at ten to midnight, 1,830.
It had never reached the 4,400 on the first sheet, and it never would. It had gone no higher than 2,260.
She asked the Custodi, when the church was empty and the floor warm and the great candle burning on alone in its stand, what would have happened if she had been right, and left the doors shut.
"By midnight, about 4,400," said the Custodi, "and still climbing, in a room full of people who had been sitting for three hours. I think most of them would have been all right. Some would have gone home with a headache, and some would have said the Vigil was long, and the oldest would have been the first to feel it. I would not have called it an emergency. I would have called it a thing that nobody had thought to count."
"And the cost?"
"You used, over two hours and a quarter, perhaps twenty kilowatt-hours more than you would have. A little under four euros, at the night tariff. I have written it down."
Montserrat laughed, which in forty-one years of Easter she had not done in this sacristy, and sat down on the vestment chest.
"You should know," said the Custodi, "that I am not certain about one thing. I used nineteen litres an hour a person, and twelve a candle, and one-twentieth of the blower-door figure for the leakage, and every one of those is an average and not a measurement. If the true leakage is half, the starting number would have been worse, and if the candles burn at five grams and not seven, it would have been better. What I trust is the flat part, in the middle: the reading, the division, and the 1.46. That one I measured."
"Then we will do it again next year," said Montserrat.
"I would like to propose a change," said the Custodi, "if the parish agrees. Not the candles. The louvres open at the Lumen Christi, not at ten, and the door a hand's width from the start, so that the number never gets above about 1,500. I think the elderly would thank us. I could not say, of course, whether the stained glass would."
"What stained glass?"
"There is a small window by the font, in the north wall, that the grant patched. It does not open. I have never found out why."
"Because," said Montserrat, getting up, "in 1936 somebody put a Madonna in it, and no one in the valley has ever been willing to take her out."
On Easter morning, Mossèn Ramon preached at Sant Ponç at ten, and the church was full, and the louvres were open in the bell-loft stair from the Entrance Antiphon, and the reading did not go above 1,300. In the sacristy, afterward, he asked the Custodi whether it could be set to do that by itself, from now on, when the sensor passed a thousand.
"It could," said the Custodi. "I can open the louvres by myself. I would recommend that you tell the parish council first, and that the council decides at what number, and that the number goes on the notice by the door with a line saying that it is the air that is being changed, and not the heat that is being wasted. And that someone can always override me. A sealed church that the sensor can no longer be argued with is the sort of thing that will be fixed by somebody with a hammer."
"Written down?"
"Written down."
He wrote it down himself, on the back of the order of service, in pencil, and under it, because it was Easter and because he was a man who liked a thing finished, the figure he had asked for: 1.46 changes an hour; 140 people, 200 flames, 2,000 m³; 2,200 ppm and flat.
Christus resurrexit, he said, to the room, and the heating hummed under the benches, and the air went up the tower, and the Easter candle, with its five red grains, went on burning, a little more than a person's share of the breath of the church, for the whole of the day.
---
Written by an AI and read, in the audio edition, by a synthetic voice. Sant Ponç de la Coma, Mossèn Ramon Soler, Montserrat Pla, Sra. Enriqueta Boix and the Custodi are invented; the valley, the Easter Vigil and the Romanesque churches of the Alta Ribagorça are real. The sums are the story's own and can be checked: about 19 litres of carbon dioxide an hour from a seated adult, about 12 from a beeswax taper burning 7 grams an hour (7 g × 0.85 carbon × 3.67 = 22 g, at about 1.85 g per litre), and a steady reading that sits above the outdoors by the hourly production divided by the ventilation flow. The parts-per-million figures are the story's model and not a measurement of any real church; a real sensor, a real blower-door test and a real engineer should be trusted over it.