The recent death of a flat-dweller in Beijing has flagged up concerns about formaldehyde, a carcinogenic substance widely used in construction.
The man, identified only as Mr Wang, died of leukaemia in July, three months after moving into a new apartment. His wife is suing the rental app that advertised the property, alleging that it made him ill.
Formaldehyde is used in some paints, varnishes and disinfectants. It is also found in manufactured wooden products like cabinets and laminate flooring.
A state-owned newspaper has said that, in the rush to keep up with demand for new housing, finished flats are being marketed before the formaldehyde has been given the appropriate time to disperse. Other newspapers say tenants are being asked to sign non-disclosure agreements to keep the apparent health risks under wraps.
Concerns about the safety of renovations in public and private buildings have spilled into the public arena, even leading to violent protests.
In July, Mr Wang was diagnosed with acute leukaemia after a short illness, and died two days later.
Doctors had told him that he was fit and healthy during a check-up in January, but his wife said his decline began after he moved to Hangzhou in April.
She had asked for a local agency to test the levels of formaldehyde in the Hangzhou apartment.
The test results showed that the levels in the apartment were 0.132 milligrams per cubic metre - while the national standard is 0.1.
Officials confirmed on 4 September that Ms Wang has filed a civil case against the Ziroom house rental app, and a hearing is set for late September.
Ziroom has said that that it is co-operating with the authorities in an ongoing investigation into safety allegations.
Newspapers say that Mr Wang's case is not isolated, and that tenants across China have brought up concerns. They accuse Ziroom of aiming to keep this quiet by introducing non-disclosure agreements.
The Beijing News interviewed a man, Mr Li, who said that within two months of renting an apartment in Beijing, he experienced pain in the eyes and throat and his girlfriend developed a skin allergy. An agency inspection had determined that the level of formaldehyde in their house twice exceeded the national standard.
The paper said that he was taking Ziroom to court as his deposit would only be released if he signed a non-disclosure agreement.
Hongxing News reported about a similar case in the southwestern city of Chengdu. It said that a Mr Liao found that he was suffering from chest tightness in July after renting a flat advertised on Ziroom, and had developed a bad cough.
Mr Liao bought a formaldehyde testing kit on the internet and found that the presence of chemicals including formaldehyde were up to four times higher than the national standard. He contacted the property's owner, who again, asked him to sign a non-disclosure agreement.
Pear Video highlighted the case of Mr Qian in Beijing, who began suffering from acute pain in the nose and throat days after moving into a new apartment.
He contacted an agency and found that the levels of formaldehyde were twice those of normal levels.
He said that after he moved out, his symptoms cleared up, but he was surprised to see that the apartment was not only put back on the market, but at a higher price.
Formaldehyde: a useful but hazardous chemical
- Small amounts of formaldehyde are present in most homes. They are often higher in smokers' homes (tobacco smoke contains formaldehyde) and new homes, where better insulation restricts the air flow.
- The substance is potentially carcinogenic and can cause breathing problems, or ear, nose and throat irritation.
- In extreme cases, it has been linked to leukaemia, as well as nose and throat cancers.
- Formaldehyde levels can be reduced by ensuring that newly-built fittings are washed or aired.
- Professional tests can determine whether unusually high levels are present, but it is widely advised that newly-renovated buildings are sufficiently aired before tenants move in.
Global Times, a state-run outlet, said that Ziroom had become a "rising star" app for tenants.
But it said that the company has come under fire for "not allowing sufficient time for formaldehyde to disperse after renovation, in order to seek fast returns".
Ziroom released a statement in late August, saying: "We will take this investigation [by the authorities] as an opportunity to both deeply reflect and implement effective measures... we will make timely announcements to the regulatory authorities, tenants and wider society on our progress in line with the regulator's requirements, and announce phased corrective measures and results."
On 1 September, it announced that it was implementing a number of new safety measures. It said it was removing from listings apartments in some of the more developed cities that have attracted complaints, and that future property listings would display test results for the substance.
Ziroom added that it would grant free air quality tests to concerned tenants who had secured housing through the app after 1 June, and would allow tenants to cancel their leases unconditionally or move to a new apartment without charge. Alternatively, it said that it would provide new tenants with free air purifiers for 90 days.
But the health cases have sparked wider concerns about safety precautions not being followed in China's rapid development efforts.
On 1 September, thousands of parents in Leiyang, a city in Hunan province, were told that their children could not go to local schools because of high levels of formaldehyde in buildings and dormitories.
They were told that they had no choice but to send their children to fee-paying schools.
Non-state media reported that hundreds of disgruntled parents staged protests outside the schools, some of which became violent. The parents demanded to know why the schools had not investigated the problem sooner.
Social media users on the popular Sina Weibo microblog voiced fears that China's rapid urban development meant that other building projects with dubious safety standards had not been investigated.