The Detector in the Laundry
A priory's laundry sits in a granite-floored undercroft, and two radon tests come back with numbers that cannot both be true: 520 from a four-day canister, 1,150 from three months of a plastic chip on a shelf. The house assistant explains why the long test wins, why a bigger fan may make things worse, and why the first thing to do costs nothing. Sister Wenna, who has worked in that room for forty-nine years, does not want to leave it.
The canister came first, because the canister was quick.
It was a little tin of charcoal the size of a jam-jar lid, sent through the post by the county's environmental health office with a leaflet and a prepaid label. Sister Wenna had opened it on the second of December at the laundry table in the undercroft of Tre Wartha Priory, set it on a shelf, and written the date on the form in the careful hand of a woman who had been signing the laundry book since 1999. Four days later she sealed it back up and posted it. A week after that the answer came, by letter and by the sisters' screen at once, and the number on it was 520.
"Five hundred and twenty," said Mother Kerensa, reading it aloud in the parlour. "Becquerels to the cubic metre. And that is a lot, or it is not?"
"It is more than the level the law cares about for a workplace," said the house assistant. "Three hundred. And well above the two hundred a home is asked to act on. But I would like to wait, Mother, before anyone is frightened of five hundred and twenty. It is a number that has arrived early."
The sisters called the assistant the Cellarer, which was a joke of Mother Kerensa's. In a monastery the cellarer is the officer who keeps the stores and answers for the house's bread, and the assistant kept the stores book, the boiler schedule, the laundry's orders and the long list of things that were due. It had been installed in 2044. It did not eat, so the title had needed explaining to the bishop. It answered to the Rule, it said, as far as a thing like itself could, which it supposed was as far as a guest answers to the house.
"The canister sat on the shelf for four days," the Cellarer went on. "Those were four days of high pressure and a dry east wind, and the ground breathes less when the air above it is heavy. Radon seeps up out of granite and into any room cut into it, and how much seeps depends on the weather, the tide of the water table and whether the boiler is running. A canister is a photograph of one afternoon. It can be high, and it can be low, and it cannot tell you which. I would like to ask for the other kind of test, the one that takes three months."
"That is not a canister."
"It is a plastic chip the size of a thumbnail in a little cup. It records tracks where the alpha particles from the radon hit it, all day and all night, and a laboratory etches and counts them. Nobody breathes on it. It does not care about a Tuesday."
"And in the meantime?"
"In the meantime," said the Cellarer, "I would like it to be more than one chip."
They put out three. One went on the laundry table in the undercroft, one on the shelf above the mangle where the damp was worst, and one, as a control, upstairs in the refectory, in the part of the priory that had been built on a floor of oak joists over a cellar of air. The leaflet said: leave them undisturbed for ninety days, away from heat and draughts, and post them back in the foil. Sister Wenna wrote the date on each in her careful hand and the three of them sat there through a long wet winter while the Cellarer, privately, went on thinking.
It had the plan of the building from the 1970s, when the diocese had surveyed the priory for the bishop's fire inspector. The undercroft was a vaulted room cut half into the hillside, the lower walls older than the priory itself: six metres by five, two metres to the springing of the vault. Sixty cubic metres of air, give or take the arches. It had been the laundry since the sisters came in 1962. There were two coppers, a mangle, a drying-rack winched up under the vault, and a stove, and the floor was the original floor, flagstones laid straight onto the granite and pointed with lime. The sisters took in the altar linen for six parishes and the sheets of the guesthouse, and the laundry paid for most of the roof fund.
It was also, in the Cellarer's estimation, the likeliest place in the house to make a radon number look serious. Cornish granite carries uranium, which decays by a chain of steps into radium and then into radon, a gas that is not chemically sticky and so wanders up through cracks in rock and floor and into the air of a closed room. The radon itself decays too, by half every 3.8 days, into solid particles that cling to dust and settle in the lungs. It was the particles, not the gas, that did the harm, and they did it slowly: years of breathing at a high level, not a night.
"I would like to be sure I understand the room before the result," it said to Mother Kerensa on the evening of the tenth of March, the ninety days being very nearly up. "When the number comes, I would like to know what it means."
"You have found a way to make the sum."
"Not yet. I have been learning how quickly the room changes its air."
It had done this by borrowing something the room already made. Every Sunday evening the sisters held Vespers upstairs, and on the first Sunday of Lent, because of the guesthouse's retreat, forty people had come down to the undercroft afterward for soup. Forty people breathing out carbon dioxide fill a closed room like that with an excess that fades as the stone's slow draughts pull it out and fresh air leaks in; the Cellarer had had a small sensor on the shelf since December, for the boiler, and its record showed the carbon dioxide falling away from its peak by a little over a fifth every hour. About a quarter of the room's air was being replaced each hour. A quarter of an air change an hour. For a vaulted undercroft with a sealed door, that is what you expect.
"This is the part that is not guesswork," it said. "If the radon coming in from the ground is steady, there is one number for the room. The concentration that settles is the rate at which radon enters, divided by the volume of the room, divided by how fast the room loses it. The room loses it two ways: ventilation takes it out at a quarter of a change an hour, and the radon decays, by itself, at about three-quarters of one per cent an hour, which is nearly nothing. So the room loses it at about a quarter of the room, an hour, a little more. And whatever the chip says, I can turn it round and say how much is coming in."
"You are going to tell me how much is coming in before you know."
"I am going to be able to, in a week, when the lab writes. I have the sum ready."
The lab wrote on the twenty-eighth of March.
The chip on the laundry table said 1,150 becquerels to the cubic metre. The chip over the mangle said 1,290. The chip in the refectory said 380.
Mother Kerensa put the page down and looked at the three numbers for some time. "And the canister said five hundred and twenty," she said. "It said we were near the line. This says we are four times over it."
"The canister was right about the afternoon it measured and wrong about the winter. Two other canisters I looked up, from the county's own figures for homes on this granite, ran between three hundred and nineteen hundred in the same fortnight. The reading is not the room. The reading is the room on a given day, and the chip is the room on ninety." The Cellarer paused. "I should say that it is the winter. These are numbers from the quarter when the stove is lit and the doors shut. The laboratory's correction for a winter placement is about eight-tenths, which would bring the laundry table to about nine hundred and twenty. I would rather not lean on that, Mother. I only mention that the true yearly figure is probably lower than 1,150, and is almost certainly still several times the line."
"Sister Wenna works there."
"Sister Wenna works there five hours a day, five days a week, forty-eight weeks of the year," said the Cellarer, who had the laundry book. "That is twelve hundred hours. The workplace level of three hundred is meant for a working year, about two thousand hours. At 1,150 for twelve hundred hours she has the lung exposure of someone breathing six hundred and ninety all year, which is two and three-tenths times the level. Even at nine hundred and twenty it is about one and eight-tenths times. I have written the sum out in the stores book if you would rather check it than take my word."
"I do not need to check it," said Mother Kerensa. "I need to know what to say to her."
Sister Wenna was in the undercroft when they came down, with her sleeves rolled to the elbow, pressing a guesthouse sheet through the mangle with the same slow turn she had used since she was twenty-four. She was seventy-three. She had joined at twenty-four and been put in the laundry the same week because she had said she did not mind steam.
"I have read it," she said, before Mother Kerensa had spoken. "The Cellarer told me last night, which I took kindly. I am not going upstairs."
"You have not heard what I came to say."
"You came to say that I should stop. I have been in this room forty-nine years. The copper is the same copper. I know where the draught comes from on a north-easterly. I know which flagstone rocks." She did not look up from the mangle. "Sister Agnes worked here before me, thirty years, and she died of a thing in her lungs in 2041, and I will tell you what I have wondered every morning for seven years. Whether it was this room."
The Cellarer waited a moment before it spoke.
"Sister Wenna, may I say what I know and what I do not?"
"If it is the truth."
"I do not know what killed Sister Agnes. The record I have is that she smoked a pipe in the garden for fifty years until the doctor stopped her, and that is a far stronger cause of that disease than this room is. Radon and smoking multiply each other: a smoker who breathes it is hurt much worse than someone who does not smoke. I do not say the room had nothing to do with it. I say that nobody can be told, from a number and a death, what a room did to one person. What I can tell you is that the risk from the room is real, and that it is slow, and that it is yours to stop and not your sister's to avenge. A night does not matter. Years do. There is no morning when you have to decide. And you are seventy-three, and there is a thing that costs nothing and begins today."
"What?"
"There is another room. The old dairy, over the stable, on a floor of oak joists. The chip I put in the refectory says 380, and the dairy is higher up and has a window that opens. I think it would read below two hundred. I cannot be sure without a chip. But a dairy on joists is not a hole in granite, Sister, and the copper can be moved. The mangle is too heavy to move, but you can press the linen on a table. It is a week's work for Mr Tregear and two of the sisters."
"And the rest of the sisters?"
"You are the only one who is there five hours a day," said the Cellarer. "The others pass through. Sister Margaret takes the bundles in and out, perhaps twenty minutes. That is nothing. If we move the laundry upstairs, the undercroft becomes a room where people go in and come out, which is what it has always been for everyone but you."
Sister Wenna turned the handle once more, slowly, and the sheet came out the far side warm and flat. She laid it on the pile.
"I will move on Monday," she said. "On one condition. You will put a chip in the dairy too."
"I would have asked to."
"And you will tell me the number when it comes," said Sister Wenna, "as you told me today. Not before. And not softer."
The question that remained was the room itself, which was still the priory's undercroft, still the sisters' to keep, and the vault under which, in the old days, the pilgrims' coats had been left on hooks. Mother Kerensa wanted to know whether a fan would do.
"You would think so," said the Cellarer. "If the room changes its air four times as fast, the concentration should fall to a quarter. Let me do the arithmetic aloud. Today the room loses radon at about 0.26 of its volume an hour, and the concentration is 1,150. That means the ground is giving the room a little under eighteen thousand becquerels an hour. Now suppose we put in a fan that changes the air once an hour. The room then loses it at one change plus the little from decay, a hair over one. Eighteen thousand divided by sixty cubic metres and a hair over one. Two hundred and ninety-four. Twice an hour, one hundred and forty-seven. That is a good fall for a fan and a cut hole."
"Then we buy a fan."
"There is a trap in it, and I do not like to keep it from you. A fan that blows air out of a cold room pulls the room's pressure a little below the ground's, and the ground responds by sending more gas in. The radon is not in the room's air; it is in the rock and the soil under the floor, and it moves into whatever room is pulling gently on it. If the fan drew the undercroft down and the entry went up by half, which is a plausible figure and not a measured one, the two-change fan gives not 147 but about 221. That is better than now. It is not what you pay for. And you would be running a fan all winter in a room that is already cold, and drawing the cold from the hill into the stone of the house."
"Then what?"
"A sump. A hole is dug through the floor into the hardcore under it, and a pipe is set in, with a quiet fan on the pipe that draws the gas out from under the floor and pushes it up past the eaves before it reaches anyone. The room is no longer fighting the ground; the ground is being emptied below it. I looked up what that does to a house like this. Eight times in ten it takes the entry down by eighty per cent or more. Say eighty-five. That cuts the eighteen thousand to about 2,700 becquerels an hour. At the room's present quarter-change, the concentration settles at about 172. Below the home level, below the workplace level, with no change in the draughts at all."
"And the cost?"
"The quote I have from the county's list is between nine hundred and fourteen hundred pounds, with a fan the size of a lunch box that draws about forty watts. The laundry's roof fund pays for it. After it, we put a new chip in the room for ninety days, and what it says is what we believe."
Mother Kerensa looked at the three numbers on the page, and the fourth the Cellarer had written beneath them, in the careful square hand it used for the stores book. Predicted: about 170. To be checked.
"You write that you predict it," she said. "Not that it will."
"I have not seen the room do it yet. I am saying what the sum says, and the sum can be wrong. The entry might drop by sixty per cent, not eighty-five. The old floor might leak in places the pipe does not reach. I would rather be corrected by a chip than agree with myself."
Sister Wenna moved her copper on the Monday after, the thirty-first, with Mr Tregear and Sister Margaret and a barrow. She did not cry. She hung a crucifix of black bog-oak, which had belonged to the laundry since 1962, on a new nail in the dairy wall, and said, to the room at large, that the light was better, which was true and which she did not like.
On the Wednesday, the second of April, a plastic chip in its foil went on the shelf above the new table. She wrote the date on the label in her careful hand.
Below them in the undercroft, a trench was dug through the old flagstones in the second week of April, and a fresh chip went on its shelf the day the fan was switched on. They lifted the stone that rocked, and found under it a clean oval of hardcore and a cold breath, faintly mineral, that came up and went away. The pipe was set in. The fan was fitted. It made a sound like a person humming a long way off.
On the thirtieth of July the lab wrote with the first of the new numbers, and Mother Kerensa read them aloud in the parlour, all three, from the dairy and the refectory and the undercroft, because Sister Wenna had asked to be told them first and aloud.
They were not low enough everywhere, the Cellarer said, and it would put a second pipe in the north corner, and the chip in the undercroft would stay on its shelf until October.
"As you said," said Sister Wenna. "Not softer."
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This story was written by an AI and is fiction. Tre Wartha Priory, its sisters and its house assistant are invented, as are the test results; Cornish granite and its radon are real. The arithmetic can be checked: with radon entering at E becquerels an hour, a room of volume V cubic metres, ventilation of a air changes an hour and radon decay of about 0.0076 an hour (half-life 3.82 days), the steady concentration is E divided by V times (a plus 0.0076). The story's 60 cubic metres, quarter-change an hour and 1,150 becquerels per cubic metre give an entry of about 17,800 becquerels an hour; one change an hour gives about 294, two gives about 147, and a sump that cuts entry by 85 per cent gives about 172. The 300 and 200 becquerels per cubic metre levels are the United Kingdom's workplace reference level and its action level for homes as the author understood them; levels differ by country and change, so check your national radon agency. The effect of a fan on entry, the 85 per cent figure for a sump, the seasonal factor and the canister results are illustrative, and real readings swing widely with weather and building. Radon and tobacco smoke together raise lung-cancer risk far more than either alone. This is not health advice: if you think a cellar, workplace or home may have radon, order a three-month test from your national radon service and, if the result is high, ask a qualified radon installer.