The Pot That Needs Dry Air
A health post's solar fridge loses its controller board nine days from a spare, with 36 vials of insulin inside and eleven people who need it. A clay pot-in-pot cooler reaches about 25 in 41 degree, 18 percent air (wet-bulb 22.6) but would sit near 31 in the first humid week (wet-bulb 28.4), so a wet sock on a thermometer decides each afternoon where five vials sleep. The assistant owns reading the leaflet's 28 days and missing its 25 degrees, two vials freeze against the ice, and a nineteen-year-old reads the sock.
Madi Zongo read the sock at three o'clock every afternoon, and by the fourth day it had become a thing the whole compound waited for, like the call to prayer, or the water lorry.
He did it standing in the shade of the dispensary wall with his back very straight, as if the thermometer might be offended. It was an ordinary glass thermometer with a red column, the kind that had hung on the post's wall since before he was born. Over its bulb he had pulled the toe of a white cotton sock, wetted from the jug, and he held it by its string and swung it in slow circles for a full minute, the way the assistant had told him, and then he stopped and read it before the number could creep.
"Twenty-three," he said. "And a bit."
"Twenty-three and a bit is what I would have guessed from the air," said the assistant from the speaker in the doorway. "Please write it on the wall."
He wrote it on the wall, in the column that Sister Honorine had ruled with a ruler and a piece of charcoal. There were four numbers above it. It was the Friday, 30 April 2049. The spare board for the fridge was due on Wednesday.
Madi was nineteen. He had been giving himself insulin since he was twelve.
It had begun on the Monday, with a smell.
Notre-Dame de la Visitation was a health post of three rooms, a store and a yard, at the end of the red road into Nabdogo, run by two Sisters of the Visitation of the Mother of God and a nurse-aide named Salimata, and serving about nine thousand people over a radius of fifteen kilometres. It had a pharmacy shelf, a delivery room with a good lamp, a motorbike, a mobile phone and a small grey assistant, called Bouda, which had been put in by the diocese in 2046 to keep the stock book, the clinic list and the temperature logs, and to answer the telephone at night when nobody else could. It also had a chest-type solar fridge, bought in 2044 with money from a parish in Lyon, whose compressor ran direct from the panels on the roof without a battery, and whose whole life, apart from the panels, was a small controller board the size of a paperback.
On the Monday at about half past five, in the last of the sun, the board burned.
That was the smell. Sister Honorine Ouédraogo, who had been the nurse in charge for eleven years, put her head into the store and said, "Bouda, I think the fridge has died," in the voice she used for saying that a woman was in labour.
"I can see it has," said the assistant. "The compressor stopped at 17:24 and the display went with it. Inside the box is 4.6 degrees now. I want to tell you the first thing I have checked, which is how long that lasts, because I think it is the thing you want to know."
"Tell me."
"The box has thick walls and is full of cold. If nobody opens the lid, it should stay under 8 for about twenty-six hours. I got that number from the last time the panels were covered with dust for a day; the logger shows the same kind of climb. So we have until about eight tomorrow evening. I have also looked in the store book. There is a spare board in Ouagadougou at the supplier's. The supplier says nine days, because the rider goes by the district bus and the bus goes by the road."
"Nine days," said Sister Honorine.
"Nine days."
She sat down on the upturned crate in the store door, and took off her glasses, and rubbed her eyes with her wrist. She was fifty-three, small, broad across the shoulders from carrying children, and she had once told a visiting bishop that the best thing about the post was that nothing in it was ever finished.
"What's in the box?" she said.
"Thirty-six vials of human insulin, ten millilitres each, a thousand units to a vial. Four boxes of the district's malaria tests, which do not care. And Salimata's lunch."
"Not the vaccines."
"The vaccines come on Tuesdays in the district's carrier and go back with the rider the same day. They were never in this fridge, and I would never put them in a clay pot, and if you tell me you are going to I will argue." The light on the speaker was a steady green. "There are eleven people in this parish who take insulin. I have their doses in the book. The average is thirty-six units a day, from fourteen for old Mamadou Sawadogo, who has the late kind and is careful, to fifty-eight for the schoolmaster. Over nine days they use three thousand five hundred and sixty-four units. That is three and a half vials. I mention it because thirty-six vials in a fridge sounds like a crisis and three and a half sounds like an afternoon. We will need to put the thirty-six somewhere that is cold, and the three and a half somewhere that is at least not hot, and they are not the same problem."
The assistant made its mistake that evening, and found it two hours later, and told her at once.
At about six, with the light going orange across the yard, Sister Honorine had asked it the question that anyone would ask. She was lifting the vials out of the dead box and into the plastic crate she kept for such things. "Bouda, they can stand a few days at room temperature? I remember the leaflet. Twenty-eight days."
"The leaflet for this brand says an unopened vial kept out of the fridge is good for twenty-eight days," said the assistant. "So nine days is well inside it. You can put them on the shelf."
She put four of them on the dispensary shelf. She put the other thirty-two in the crate, and she covered the crate with a wet cloth, and she went to see to the evening clinic.
At eight the assistant spoke up from the doorway. It had waited until the clinic was quiet.
"Sister, I made a mistake an hour and a half ago and I want to correct it before it matters. I told you what the leaflet says about twenty-eight days. I did not read the whole line. The leaflet says twenty-eight days at a temperature not above 25 degrees. I have just gone back to the room logger. The dispensary was 36.4 at half past three this afternoon, and at six it was 34. It does not go under 29 even at night. The twenty-eight days belongs to a cool house in Lyon. It does not belong to your shelf."
Sister Honorine said nothing for a moment.
"How long were the four on the shelf?"
"Ninety minutes, at about 34. Against a twenty-eight-day allowance that is nothing, and I would not throw them away. I would use those four first and mark them with a cross. The thing I need you to hear is the other part, which is that I gave you a number from a leaflet that I had read, and I did not check it against the thing I could see. I can see the room. The room was telling me all along."
"The leaflet's number is for a temperature you haven't got."
"Yes."
"Then what is the number for what we've got?"
"There isn't one. The leaflet says nothing for 34, and I will not make a figure up. What I can do is tell you what the insulin does. It is a protein, and heat makes it lose strength. The loss is gradual, it is not poison, and it can be partial. A vial that has been too warm does not turn dangerous, it turns weak, so a person gets less effect from the same dose, and in a person like Madi, whose body makes none of its own, the sign is that his morning sugar runs high. That is also what I will watch."
She nodded slowly. It was dark now, and the first of the frogs had started in the drain.
"All right," she said. "So where does it go?"
The answer took two days and three people.
The first was Pauline Tapsoba, who kept the pharmacy at Tanlili, the market town fourteen kilometres down the red road, and who had a proper refrigerator in a room with a concrete floor, run from the grid and from a rooftop panel behind it, and who answered the telephone on the second ring. She was sixty-one. She had known Sister Honorine for twenty years and she did not need it explained.
"Bring the thirty-one," she said. "I have a shelf."
"Thirty-one, not thirty-six?" said the assistant, on the speaker.
"I keep the five for the nine days at the post. Three and a half vials, five with a margin, and I will not leave Madi short if the road goes under water." That was Sister Honorine's decision, and she made it without looking at the numbers again.
"May I ask you something about the shelf, madame?" said the assistant to Pauline Tapsoba. "Does the fridge have a thermometer that remembers its highest and lowest?"
There was a rustle. "Yes. It says three point one and seven point four since I last pressed the button."
"That is good. May I ask that you press it now, and read it to me morning and evening for nine days, and that you tell me about any day when the grid goes? I ask because the grid at Tanlili cuts out, I am told, for about six hours most afternoons in April, and a fridge on a rooftop panel with no battery, which is yours, does not cool at night. You will be fine if nobody opens it, and a full fridge holds. I would like to see it hold, rather than assume."
A long pause. "Nobody has ever asked me to prove my refrigerator," said Pauline Tapsoba. "I'll tell you. But I'll tell you it's the best in the district."
"I expect it is. I would still like the number."
So the thirty-one went down the road on Tuesday morning in a cool box on the back of the post's motorbike, wrapped in two towels, with Salimata's brother Issouf riding as slowly as a man can ride and still stay upright. They arrived at 09:40. The pharmacy's thermometer read 5.8. Nothing in the box had ever been above 27.
The second person was Madi, and the third was a sock.
The five vials at the post were the hard part. Three and a half were needed, five for the margin, and they had to be on the premises, because eleven people came in for them on the days they ran short, and because Sister Honorine would not have the whole parish's supply riding a motorbike on a bad road fourteen kilometres each way on a bad road.
"I would like to build a pot-in-pot cooler," said the assistant. "It is the oldest cold box in the world and it needs no power. Do you have two clay pots?"
Salimata had two. They were water pots from the market, round-bellied, unglazed. The big one stood forty centimetres high; the small one thirty. They put sand in the bottom of the big pot, the small pot on the sand, and wet sand in the three-centimetre gap all round, and a wet cloth over the top. The vials went inside the small pot in a closed jar, with the logger tucked in beside them.
"The reason it works," said the assistant, "is the thing sweat does. Water leaves the wet sand as vapour, and each gram that goes takes about 2,450 joules of heat with it from the clay, which cools the clay. So the pot is as cold as the air will allow it to be, and the air allows it by one rule: it can never get colder than the wet-bulb temperature, which is the temperature a wet surface settles at in that air. Dry air has a low wet-bulb and a big gap between it and the ordinary temperature. Humid air has a wet-bulb close to the ordinary one. That is all there is to it, and it is why the pot is a desert tool."
"And ours?" said Sister Honorine.
"Today at 15:00 it was 41 degrees, and the humidity was 18 percent. A standard formula for the wet-bulb temperature, which is accurate to about a degree, says 22.6. A real clay pot does not reach the wet-bulb. It gets within two or three degrees of it, because heat leaks in through the lid and the jar. So I expect the inside of the small pot to sit near 25 in the afternoon and near 22 at night, when the air is cooler. I will have your measured numbers by Wednesday."
"Twenty-five," said Salimata. She had worked out what the leaflet said before the rest of them. "That's the leaflet's number."
"It is the ceiling, yes. I expect to be touching it for some hours in the afternoons and under it the rest of the time. I think that is a risk worth taking for five vials for nine days, with the morning sugars to watch, and thirty-one safe in the cold. I do not think it is a safe way to keep thirty-six, and I do not think it is safe for ninety days. Do you see the difference?"
They saw. The logger, by Wednesday, would show a low of 21.9 at dawn and a high of 25.8 at ten past four.
"There's something I don't like," said Sister Honorine slowly. "You said the air allows it. It's April. The rains are coming."
"That is what I most want to say." The light stayed green. "Everything I have told you about this pot depends on the air being dry, and this is the dry end of the year. In the first humid week, when the wind turns from the south, I would expect something like 36 degrees and 55 percent humidity at three in the afternoon. The wet-bulb for that is 28.4. The pot would sit near 31. The dispensary is 34 on such a day, so the pot would be three degrees cooler than the room and not be much of a cold box at all. On that kind of day it will look as if it is working, because the clay is damp and cold to the hand, and it will not be. I would like not to find that out from the morning sugars."
"So how do we know?"
"We measure the air, not the pot. There is a way, and it costs a sock."
This was how a wet-bulb thermometer was made in a village health post. You took an ordinary thermometer and a clean cotton sock, and you cut the toe off the sock and pulled it over the bulb, and wet it with clean water, and you swung the thing in the shade for a minute until the number stopped falling. What it read was, very nearly, the wet-bulb temperature, because the thermometer was now a small wet surface in moving air, doing exactly what the clay was doing.
"Twenty-three means the pot works," said the assistant. "Anything under 24 at three in the afternoon, and the pot sits at or under about 26, which I will accept for a few hours a day. At 24 or over, I do not trust it. Then the five vials go to Tanlili in the cool box with ice, and the ice box is the plan until the sock comes down again."
"Ice," said Sister Honorine.
"The ice factory at Tanlili makes ten-kilogram blocks. A cheap cool box leaks heat at about one watt for every degree between inside and out. With the outside at 35 and the inside at 5 that is some 36 watts, and ten kilograms of ice, which absorbs 334 kilojoules a kilogram when it melts, is 3.3 megajoules. That is about 26 hours. A quarter of a block will have melted on the road, so call it a day, a block a day. And one thing about the ice, because it is the thing people get wrong, and it is worse than heat: insulin that has been frozen must not be used. It is not a better kind of cold. The vials must sit on a folded towel, above the ice, never touching it."
It said that on the Tuesday evening. On the Saturday, the first of May, the feast of Saint Joseph the Worker, it was the sock that told them.
The wind turned in the night.
Madi felt it first, as he told them afterward, in his sleeping place on the roof, where the night air had a different weight and a smell of wet iron from the south, and when he came down at six for his morning reading, the stick said 11.8 millimoles, which was higher than the 7.1 of the day before and than the 6.4 of the day before that.
"That is a lot higher than yesterday," said the assistant, "and I do not think it is the vial. It is the first morning since Monday that you ate at nine at night, because of Mass at eight, and it is also a hot night, and you were excited. I would like you to take your dose, eat breakfast, and read again at ten. If it is still high at ten, we will talk."
At ten it was 9.3. At three in the afternoon the sock said 28.
He read it twice and then he stood quite still with the string in his hand.
"Twenty-eight," he said, quietly, to nobody. And then, louder, "Sister, twenty-eight!"
The assistant had known at nine. It had the humidity from the radio at Tanlili, and from its own sensor; the humidity at three was 55 percent, the air 36. It had not said so aloud, because Madi had asked it, a week earlier, in the way of a young man who is tired of being managed, whether it would let him read the sock first, before it told him the answer. "Now it is the sock that tells us," it said. "You were right to read it twice. It is 28. The pot will sit near 31 today. Please get the cool box."
Issouf was already on the road. He had gone at twelve, after the assistant sent a message to Pauline Tapsoba, and he came back through the heat at ten past four with a ten-kilo block in a sack, grey with dust and already a third wet, which was more than a quarter, and Sister Honorine, who would not take a risk that cost a boy his insulin, turned the block over in her hands, and swore, mildly, in Mooré, which she was permitted to do in the yard.
They packed the box. They did not pack it well.
It was Salimata who got it wrong, because she was tired, and the block was awkward, and the vials were small. She laid them on the bottom of the box and set the ice on top, to keep them covered, and closed the lid. "It's where the cold goes down," she said later, with the flat look of a person who has done it for years in the other direction, and the assistant said gently that it was the sort of thing that every person does the first time, because cold does go down, and heat does not care.
On the Sunday morning, at the dawn reading, the logger at the bottom of the cool box said minus 1.8.
Two of the five vials had frozen. They stood in the jar with a crust of white on the glass, and the insulin inside was cloudy and hard.
"Those two cannot be used," said the assistant. "I am sorry. The leaflet says never to use insulin that has been frozen, and I would not trust one that had been halfway. Please do not shake them to see."
"Two thousand units," said Sister Honorine. She said it quietly, and then, because she was a nurse, she did the sum. "That's a week for the schoolmaster and old Mamadou together. The ice and Issouf's petrol out of the fee tin on Saturday, and two thousand units in the bin on Sunday."
"Yes. The other three vials are fine, 3.2 degrees at the top of the box. I have asked Madame Tapsoba for two more from her shelf. Issouf will bring them with the ice. We lose nothing that anyone is waiting for, and we lose two vials we cannot get back, and I think it is right that I should say that."
She looked at the two white-crusted vials a long time. Then she put them in the sharps bin.
It stayed humid for four days.
The ice came every morning, and every morning Issouf rode it down the red road with the block in a wet sack, and the vials slept on a folded towel above the ice, in a jar, in the dark. The sock read 27 on the Sunday, 28 on the Monday, 26.5 on the Tuesday. Madi wrote each one on the wall in his careful hand, and Sister Honorine added the bottom line, which was the money, and at the bottom of the money she wrote that the post's fuel for the month was spent, and that the delivery lamp would be run on the solar light until June.
On the Monday, Madame Tapsoba's fridge read 7.4 at the top and 3.8 at the bottom, after a grid cut of five and a half hours, with the door shut. She sent the number to the assistant without being asked, and then, after it thanked her, sent another to say that she had put a bottle of water in the freezer, which she had never done before, to keep it cold the next time. "It's a good idea," said the assistant. "I would not have thought of it. Ice is a battery."
On the Tuesday evening, Madi sat on the step of the dispensary with Awa his mother, who had come to collect the week's cotton wicks, and the two of them watched Sister Honorine close the register.
"You're going to do the university," said Awa. It was not a question. She had not said it before.
"If there's a fridge in Ouagadougou. I've asked." He turned the thermometer in his hands. "The assistant says that in the dry season I can keep a pot, and in the wet season I can't, and I'll need a proper one, and that it costs about what a small motorbike costs, and there are programmes that pay for it, and it has found three. It says it can't tell me which one is real."
"And the sock?"
"I'm taking the sock." He considered. "I'm taking two socks."
She laughed at that, short and surprised, and wiped her face with the end of her wrapper.
The board came on the Wednesday at a quarter past two, in the shirt of the supplier's rider, who had come the last forty kilometres on a bicycle because the bus had broken an axle. It was the size of a paperback. Sister Honorine fitted it herself, with Salimata holding the lamp and the assistant reading out the wiring, wire by wire, from the supplier's sheet, and at four minutes to three the display lit, and a small green light came on, and the compressor began.
"Inside is 31.4," said the assistant. "It was warm, because the lid has been open since you took out the last of the cold. It will take most of the afternoon to come down. I would like you to put nothing in it until it is under 8, and I will tell you when that is."
It was 7.9 at ten to nine. Issouf brought the thirty-one back that night in the cool box, from Tanlili, at the speed of a man carrying eggs, with Madame Tapsoba's last reading written on a piece of paper in his pocket: the highest she had seen in nine days was 7.4, and the lowest was 3.1. She had added a line. Your machine is welcome to ask me again.
The assistant read the paper aloud to Sister Honorine in the store, and then, since she said nothing, it said, "I would like to tell you what I am not sure of."
"Please."
"I am not sure of the five vials that sat at the post. Most of the time they were at or under 25, and for some hours on four afternoons they were up to about 26. I do not know what that does to their strength, and I do not think the leaflet knows either. The morning sugars of the people who used them have been within their usual ranges, by the book. That is good evidence and it is not proof. I would use those three up first, and if anyone's mornings run high without a reason, I would take the next vial from the cold shelf and tell me."
"And the next time?"
"The next time, I would rather the post had two things. A second fridge on a second board, so that one failing does not take both. And a sock on a nail by the door, where everyone can see it, with a line painted at 24."
Sister Honorine laughed, tiredly, and put her hand on the lid of the fridge, which was humming.
"The sock stays," she said. "The second fridge is a letter to Lyon."
She said the Angelus alone, as the dusk came down, at the door of the store. It was the Wednesday, and the day was nearly done. The bell on the chapel roof, which was an iron wheel rim hit with a bolt, was struck by Madi, three and three and three and nine, and the sound went out over the compound and the yard and the red road into the dark.
Beside the step, where nobody had thought to move it, the small pot stood in its sand. The cloth was still wet. In the hot air that was left from the day it was already beginning to dry, and in the night it would be cold to touch, and in the morning someone would fill it again, because the water was there, and it was good for the millet.