A major privately run airline in Zambia has been using unproven badges, which manufacturers claim can offer protection against viruses.
A video posted by Mahogany Air on their Facebook page shows cabin crew wearing the badges.
Mahogany Air claims, without any basis, that the badges have "air-purifying virus buster technology that purifies the air around any passenger or crew member wearing it".
The airline's CEO, Jim Belemu, told the BBC he believed the badges worked and would offer additional protection but there is no evidence they can ward off viruses and bacteria, and some health authorities have issued warnings about them.
Similar devices are being sold around the world and at one time were worn by members of the Russian parliament. Some countries have banned them. In Africa, the president of South Sudan and other senior officials were seen using the badges although a government official told the BBC they later stopped wearing them.
The substance released by such cards or badges - the bleaching agent chlorine dioxide - is potentially harmful. In April, the US Food and Drug Administration said chlorine dioxide products had not been shown to be safe and effective for any use, including against Covid-19.
The agency says the substance, which is a powerful bleaching agent, can cause "serious and potentially life-threatening side effects".