Every Hong Kong stairwell I know has a pile of boxes in it, and the landlord always says it is only temporary. Think about that when you read that dozens of people fled a Mong Kok rooftop blaze on Tuesday.

RTHK reported the fire and the evacuation. We have no cause and no injury details. So what we know is simple: a fire on the roof, and a lot of people who had to get down and out.

Now picture it. Smoke above you, a neighbour in front of you, and one narrow stairwell. You are not thinking about fire safety. You are thinking about the person with the shopping trolley.

That stairwell is the one part of the building everyone agrees is for emergencies. It is also the part everyone uses as a cupboard. Old fans. Flattened cardboard. A rice cooker nobody will admit to owning. Each pile looks harmless on its own. Together they are the reason inspectors keep writing the same notice.

Nobody plans to block an exit. It just happens one box at a time, and the exit shrinks with it.

The Observatory has a fire danger warning in force today, 7 October. It is 27°C with 56% humidity (our city strip). Nobody will tell you to stay home, but it is dry, and dry is when roofs and rubbish catch.

So go and look at your own stairwell tonight. If there is a pile of boxes in it, you now know who left it there. The boxes will probably outlast the fire warning.