As the smoke started wafting into her corner of Malaysian Borneo from Indonesia, Elaine Sim started wearing a face mask outdoors. Then she bought four air purifiers for her home. Finally, she tried to seal her windows with tape.
Wildfires have been raging across Indonesia for weeks and have raised fears of a regional health crisis as the toxic haze has spread into neighboring countries. Outside Indonesia, perhaps the worst affected area is the Malaysian state of Sarawak, where Ms. Sim lives in the capital, Kuching.
“The haze is everywhere, like in a horror movie,” she said. “When you walk in hotels and restaurants in Kuching, you can see the haze inside, too.”
Last week, the Air Quality Index in Kuching reached 457, according to monitoring company IQAir, a hazardous level that forced the authorities to ask people to limit outdoor activities. They also declared a state of emergency for the town of Serian, near the Indonesian border, which recorded an A.Q.I. of 832. (The U.S. Environmental Protection Agency classifies an AQI reading of 50 or below as “good,” meaning air quality is satisfactory.)
In recent days, the Malaysian government has spent the equivalent of more than $100,000 on cloud seeding in an effort to make it rain in parts of Sarawak and improve the air quality.
On Sunday, The New York Times gained rare access to one of these missions, aboard a Royal Malaysian Air Force transport plane that took off from an air force base in Kuching. Our destination was about 100 miles east of the city, areas near the Indonesian border.
The payload of the Lockheed C-130H-30 Hercules turboprop was four large stainless steel tanks. Each tank, holding a mixture of 1,200 liters (317 gallons) of water and 200 kilograms (440 pounds) of salt, was strapped to the center of the plane.
Saltwater helps water droplets in the cloud merge and expand until they become heavy enough to fall as raindrops. But meteorologists are divided over the effectiveness of cloud seeding because it is difficult to prove that it would not have rained anyway without the seeding.
The officials on board — a crew of seven air force officers, four weather experts and two disaster management officials — were on the hunt for the perfect cloud. They were looking for clouds about four miles tall and about five miles wide, said Mohammad Redzuan Abdul Moin, a cloud-seeding expert from Malaysia’s Meteorological Department, who was on the plane. These parameters, he said, were key for the salt particles to travel within the cloud and help form raindrops.
The officers used satellite imagery, GPS, and the plane’s weather radar to locate clouds suitable for seeding. The aircraft flew at about 7,500 feet, well below the cruising altitude for commercial airliners.
Low visibility made it hard for them to spot a suitable cloud for seeding.
But an hour later, they identified a fluffy white cloud that evoked the head of a cauliflower.
The crew lowered the plane’s ramp, opened the valve of the tanks and started spraying the saltwater solution into the cloud. We spent about half an hour circling within the lower portion of the cloud. Then the crew repeated the process with another cloud.
By the time we were back on the ground, it appeared that the four-hour mission had been successful, near the Batang Ai dam about 10 miles from the Indonesian border.
“There was light rain for a few hours at the dam,” said Jonny Wong Kwie Ji, an official at Sarawak Energy, the utility that runs the dams in the state.
But it was far from a permanent cure for the haze.
“Even when it rains after cloud seeding, that clears the air for a while,” said Stellios Plainiotis, who has studied long-range air pollution and is based in Kuala Lumpur, the capital of Malaysia.
A lasting solution to reduce the smoky haze requires controlling the fires in Indonesian Borneo, while air filtration can offer protection indoors, he added.
Malaysia lifted a state of emergency in Serian after the air quality improved on Monday, which officials attributed to the cloud-seeding operation. But the A.Q.I. in the town returned to hazardous levels on Tuesday.
In Kuching, Ms. Sim, who owns an immigration services agency, had also felt the economic effects of the fires.
“Haze is very costly for households,” she said. “I had to close my office in the first week of September, too, due to the haze.”
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