But even in their most addled moments of envy, ordinary Beijingers could take some comfort in the knowledge that the soupy air they breathe on especially polluted days also finds its way into the lungs of the privileged and pampered.

Such assumptions, it seems, are not entirely accurate.

As it turns out, the homes and offices of many top leaders are filtered by high-end devices, at least according to a Chinese company, the Broad Group, which has been promoting its air-purifying machines in advertisements that highlight their ubiquity in places where many officials work and live.

The company’s vice president, Zhang Zhong, said there were more than 200 purifiers scattered throughout Great Hall of the People, the office of China’s president, Hu Jintao, and Zhongnanhai, the walled compound for senior leaders and their families. “Creating clean, healthy air for our national leaders is a blessing to the people,” boasts the company’s promotional material, which includes endorsements from a variety of government and corporate leaders, among them Long Yongtu, a top economic official who insists on bringing the device along for car rides and hotel stays. “Breathing clean air is a basic human need,” he says in a testimonial.

In some countries, the gushing endorsement of a well-placed official would be considered a public relations coup. But in China, where resentment of the high and mighty is on the rise, news of the company’s advertising campaign is stirring a maelstrom of criticism. “They don’t have to eat gutter oil or drink poisoned milk powder and now they’re protected from filthy air,” said one posting on Sina Weibo, the country’s most popular microblog service. “This shows their indifference to the lives of ordinary people.”

News that Chinese leaders are largely insulated from Beijing’s famously foul air comes at a time of unusually heavy pollution in the capital. In recent weeks, the capital has been continuously shrouded by a beige pall and readings from the United States Embassy’s rooftop air monitoring device have repeatedly registered unsafe levels of particulate matter.

But those very readings, posted hourly on Twitter or through an iPhone app, have prompted a public debate over whether the Chinese government is purposely obscuring the extent of the nation’s air pollution. Unlike the American Embassy readings, Chinese environmental officials do not publicly release data on the smallest particulates, those less than 2.5 micrometers, which scientists say are most harmful because they are able to penetrate the lungs so deeply. Instead, government data covers only pollutants larger than 10 micrometers — a category that includes sand blown in from the arid north and dust stirred up from construction sites.

Environmental officials prefer to focus on air quality improvements of recent years, largely achieved by replacing coal-fired stoves with electric heaters and closing heavy industry in and around the capital. Driving restrictions have slightly eased the environmental injury of the 700,000 new vehicles that last year joined the capital’s jammed roadways.

But when pressed, those same officials acknowledge that their pollution metrics willfully ignore the smaller particles, much of them generated by car and truck exhaust. In fact, the American Embassy’s monitor has become an unwelcome intrusion into China’s domestic affairs, according to a diplomatic cable released this year by WikiLeaks, which said a Foreign Ministry official had requested that the Americans stop publicizing the data.

The director of the Institute of Public and Environmental Affairs, a nonprofit organization in Beijing, said many government officials feared that publicly revealing such data could stymie development or dent the image of cities that had been trumpeting their environmental bona fides.

“I don’t agree with this philosophy,” said the director, Ma Jun. “The government’s more urgent priority should be to warn the public when the air quality is dangerous so people susceptible to poor air quality, like children or the elderly, can make decisions to protect their health.”

The government does appear to be moving in that direction. In September, the Ministry of Environmental Protection said it planned to amend the nation’s air quality standards to include the smallest particulates, although it has not released a timetable for adopting the new standards.

Officials in Beijing, however, are apparently not quite ready to embrace it. In response to criticism over the heavy smog of recent weeks, a spokesman for the city’s environmental protection bureau, Du Shaozhong, assured the public that they should feel secure in the government’s own readings, which termed the city’s air “slightly polluted” even as the embassy monitor found it so hazardous that it exceeded measurable levels. “China’s air quality should not be judged from data released by foreign embassies in Beijing,” he said.

According to the Broad Group’s Web site, it did not take much to convince the nation’s Communist Party leaders that they would do well to acquire the firm’s air purifiers, some of which cost $2,000. To make their case, company executives installed one in a meeting room used by members of the Politburo Standing Committee. The deal was apparently sealed a short while later, when technicians made a show of cleaning out the soot-laden filters. “After they saw the inklike dirty water, Broad air purifier became the national leaders’ appointed air purifier!” the Web site said.