When windows fall, they can injure like a fragmentation grenade.
"They don't need a direct hit to injure because they shatter. A window is sharp, heavy and made of glass," says Mr Lee Koon Peng.
He emphasises: "And if it does hit a person directly, the consequences will be very, very bad."
Mr Lee, 55, knows his windows well. He is a senior associate engineer at the Building and Construction Authority (BCA) and has seen it all in the over 12 years of inspecting windows.
He recalls a case from 2010, when he attended to an incident involving a coffee shop cleaner.
She was injured after an upper-storey window hit a parapet on the second storey even though it landed away from her.
The glass shattered and the shards cut her leg, but thankfully, the injuries were minor.
In 2013, a falling window hit a parked car and smashed its rear window. The car was unoccupied.
In both cases, the home owners were not around.
Even office buildings and skyscrapers are not spared from poor window maintenance.
In 2009, a large window panel fell from one of the upper storeys of AIA Tower, crashing into the crowded CBD street below during office hours.
Again, thanks to pure luck, no one was seriously hurt.
Mr Lee reads out this list of incidents with a sense of familiarity.
He had attended to all these cases as it is his job to find out why it happened and how to stop it from happening again.
If necessary, the authorities can mete out severe penalties to homeowners whose windows fall due to the lack of maintenance - up to a year in jail and a $10,000 fine.
Each memory is a reminder that dangers are aplenty in high-rise Singapore and why there are lives that depend on him to do his job well.
Mr Lee says: "Even when I visit my relatives' and friends' homes during Chinese New Year, I will be checking their windows to see if they are okay. It has become a habit."
He and his small team of seven engineers in BCA's special functions group have responded to more than 600 incidents of falling windows in Singapore since 2005.
On average, Mr Lee visits about 20 units in a day.
This involves safety inspections and blitz operations on entire blocks to check for windows that are not up to code, often acting on feedback from the public, the police and HDB.
Under the Building Control (Retrofitting of Casement Window) Order 2004, homeowners are required to engage an approved window contractor to retrofit the aluminium rivets of casement windows with stainless steel rivets or screws.
This applies to windows in all residential units except for those in landed properties and the ground floor of buildings.
But while most homeowners cooperate, Mr Lee confesses that it can be difficult trying to convince some to change.
Last year, he encountered a casement window that was dangling.
"The homeowner was an old lady who lived alone and did not want to speak to us. Her town council cordoned off the common area below, while social services officers and the woman's relatives were called in to convince her," he says, adding that it took a month before she complied.
He has even seen "creative" solutions, such as a Pasir Ris home owner who duct-taped a corroded window, claiming that it was always closed.
Laughing at the recollection, Mr Lee says it took a while to remove the tape.
"There is no guarantee that someone may not open the window in future," he explains.
But there is a positive spin at least.
Ten years ago, there were over 100 cases of falling windows yearly.
That number dropped to 34 last year.
In the first five months of this year, there were 16 - 11 were casement windows and five were sliding ones.
Mr Lee says: "While there have not been any cases of injury due to fallen windows in the past five years, just one fallen window is one too many and it's an accident waiting to happen.
"I will only feel happy when there are zero cases."
SECRETS OF THE TRADE
1. There is no shortcut to the job.
Be sure to check every rivet and screw as a single loose part can lead to terrible consequences.
2. Always carry your tools around.
This includes an extendable mirror to help you peek around hard-to-reach corners of a window, and a brush to remove dust that may obscure a corroded screw.
3. When you encounter an angry or uncooperative home owner, do not lose your cool.
Explain why you have to do the checks and know that the law will back you up too.
This article was first published on June 19, 2016.
Get The New Paper for more stories.