The Hong Kong secretary for security has said that ordinary laundry procedures can handle tear gas residue that may be embedded in clothing.

John Lee was replying to written questions submitted by health services sector lawmaker Joseph Lee at the Legislative Council on Wednesday.

More than 16,000 tear gas canisters have been fired by police officers across Hong Kong to disperse protesters since large-scale protests, initially over the now-withdrawn extradition bill, started in June last year.

Photo: May James/HKFP.

Joseph Lee said that there were rumours online claiming that some frontline police officers took their uniforms – and other police clothing worn at work – to self-service laundries for washing. He said residents raised concerns over whether their own clothing washed at laundries would be contaminated.

John Lee, in reply, said police clean their uniforms at laundries inside stations which are operated by outsourced service contractors.

“Police have not received any report of discomfort or health problems on the wearing of cleaned clothing…” he said.

Photo: May James/HKFP.

Lee said tear gas contains 2-chlorobenzalmalononitrile, commonly known as CS, which will gradually dissolve in water during the washing process, according to international literature.

“The dissolved CS will be hydrolysed rapidly. This is especially so when the temperature of the water will be increased during the normal washing process and the pH will also be increased by the alkaline additives used in the washing powder, as both processes will accelerate the CS hydrolysis process,” he said.

“Generally speaking, CS has a half-life of only one minute in water of 25 degrees Celsius and a pH value of 9 with general laundry detergents in the washing process. Therefore, ordinary laundry progress can already handle CS residuals that may be stained on clothes,” he added.

Tear gas fired near Queen Elizabeth Hospital in November 2019. Photo: Stand News.

Lawmaker Lee also asked if there were special arrangements for washing clothing at Queen Elizabeth Hospital in Jordan, after tear gas was fired nearby in November last year.

Secretary Lee did not directly answer but said that, during nearby unrest, the hospital temporarily suspended the intake of fresh air to the ventilation system in specific areas, sealed off windows, and turned on indoor air curtains to reduce air infiltration. Portable air purifiers were deployed to individual wards. Environmental cleansing was arranged, and the replacement of air filters in the ventilation system and medical compressed air system has begun, Lee said.