Before yesterday, you probably think that the cool air in your room comes from your router—we non-engineers have never thought of how things work because we’re more obsessed with what shows are available in Netflix.
But I bet that since yesterday’s incident in Nex, you might be a tad more careful when you enter a room, and look up to ensure that the ceiling won’t fall on you.
What if I tell you that you shouldn’t worry about the ceiling, but you should worry about the things above the ceiling?
Then again, throw your unnecessary worry thoughts away because every building structure in Singapore is sound: like our cars, buildings need to be inspected at regular intervals by structural engineers in accordance to Section 28 of the Building Control Act.
So what happened yesterday could’ve been an unfortunate isolated incident, but if you want to be an armchair detective and speculate what could have happened, here are ten facts about ventilation ducts you probably should know.
What’s Above the Ceiling
When you look up now, you probably see a ceiling with lights.
Most of them are what we called false ceiling or dropped ceiling; it’s not a real ceiling because there’s a layer between the ceiling you see and the real ceiling that connects to the next level.
Because we’re Goody Feed, we’re not going to explain with jargons that we ourselves don’t understand, so we’ve drawn an example for you instead:
Different places would have different things on the false ceiling. For example, for our office, we’ve seen some cables for our Internet and lights, the air-con ducts and some adorable rats.
Some other places might have kept a death body there, but you get the gist: a simple one would just be full of cables and air-con ducts.
And that leads to the next point:
The Different Types of Air-Conditioners
When you think of air-conditioners, you’d think of this:
That’s understandable since that’s what we have in our homes. For this type of air-conditioner, the air is being sucked in through the little gap, and because it’s usually used for a small room, it can rotate the air in a short amount of time and keep the room cool.
Usually, because it’s not a lot of air, the ducts are usually rather small.
But if you work in a bigger office, you’d see this air-conditioner:
And this is the one that’s a tad…trickier.
Cassette Air Conditioner Ducts
Unlike wall air-conditioners, cassette air-conditioners, which are usually mounted on the ceiling, cools a bigger area, and therefore needs to pump out more air and suck in more air, too.
You can, of course, install 100 wall air-conditioners, but common sense will tell you to install 10 cassette air-conditioners instead.
The amount of area that the air-conditioner can cool is measured in what is called btu (British thermal unit): a wall air-conditioner might only be 10,000 btu, but a cassette one can go above 40,000 btu. In fact, when you buy a new air-conditioner, you should look at your house surface area and the air-conditioner btu to ensure that the air-conditioner can cool the entire area.
And as usual, the bigger the btu, the bigger the air-con duct has to be so that more air can be sucked in and released.
Which is why while a usual duct for a wall air-conditioner can look as cute as a bubble tea straw…
…the ones for cassette air-conditioner is so large, James Bond and Ethan Hunt like to crawl in them:
But this is in Singapore, whereby almost every room is air-conditioned. Are ducts used for other purposes too?
Ducts Can be Used for Ventilation Too
Yes, a duct isn’t used just for air-conditioner air but for any place that needs air circulation. Just head down to a coffeeshop and you’d see air ducts below the ceiling.
Just think of it as an extended window or an exhaust pipe: it brings the air from the outside to the inside and vice-versa.
And now that you know the functions of the ducts, let’s move on to the meat of this article: how does it work?
Suspended From Real Ceilings
Actually, if you’ve been to an industrial building or an office that’s being designed to look industrial, you’d know how it looks like.
These warehouses or offices won’t have a false ceiling to cover what’s on top of the room, so you get to see all the ducts, which used to be deemed “unsightly”.
In recent years, these designs have gained traction because of #Instagram, but in the past, some offices didn’t install a false ceiling to save cost, as false ceiling only aims for one purpose: aesthetics.
In other words, all those ducts, pipes and whatnot are actually secured to the real ceiling, usually through a cable system; so it’s unlikely that in the Nex incident, the false ceiling gave way. Instead, the ducts fell onto the false ceilings instead, and the false ceiling couldn’t hold the weight of the ducts.
But are they really that heavy?
Different Ducts Have Different Weight
There are actually three types of ventilation ducts: the flexible duct, the rigid duct and the semi-rigid duct.
The flexible duct is the cheapest and because it can be bent, it’s popular. It basically looks and works like a big hose:
However, as you can probably tell, it can be punctured if a cat crawls onto it and bites it. Not that a cat would do that but you get the idea: air leaks are common, and once it leaks, you need to get a new one.
The rigid duct and semi-rigid duct are those you see in movies, whereby characters crawl into to get to another room. Those are obviously better and stronger, and comes in parts so you won’t need to change the entire “hose” if there’s an air leak; you can just replace one section.
Now, regarding whether they can hold the weight of a person…let’s just say that there doesn’t appear to be an answer, because it’s not supposed to be for humans but for air.
How a Duct is Installed
Thankfully, I won’t need to spend hours to research on this part because BCA has a video of how it’s installed:
Simply put, it’s suspended, secured, secured, secured and secured. It’s supposed to be so secured that even if Superman flies up and break the ceiling, the ducts would still be secured.
However, do note that it’s actually a rather small duct compared to the one in Nex, so it doesn’t look heavy. Tom Cruise would’ve fallen from it if he decided to crawl into it for his next mission should he choose to accept it.
Tom, Dick & Harry Can’t Install Air-Conditioner
You might think that someone had cut corners and plucked a teenager from the street to install the air-condition system in the cinema in Nex, but that’s not possible.
According to BCA, only a trained air-conditioning unit installer can install any air-conditioning unit on the exterior of any building or which projects outwards from any building, and he or she must be certified by the Building and Construction Authority to carry out air-conditioning unit installation works.
By now, you’re wondering: so what could’ve caused the duct to fall?
Reason for a Collapse Overseas
The reason for the collapse in Nex is still unknown, but here’s one reason why a ventilation duct in a school has collapsed in the US.
Remember reading about how the ducts were supported by the real ceiling? The “support” was the culprit in an incident that happened in 2013 at Shaler Area Elementary School, whereby 13 children were injured.
The “metal cable support system failed”, and it was later revealed that cables and the catch mechanism might not be appropriate for the size of the ducts as it was meant for smaller ducts.
In other words, corners were cut and of course, someone was sued.
And here’s one interesting thing: there’s a YouTube instructional video that states that the cable system mentioned is adequate for the ducts. I seriously hope installers in Singapore don’t depend on YouTube for instructions.
Ductwork in a Cinema Hall is Very Different
Ductwork is part of a larger thingy called HVAC (Heating, ventilation, and air conditioning), and unlike the HVAC for a room, a cinema hall is drastically different.
In fact, because it’s so unique, there might be “air grilles” at the sides to ensure air supply.
Because you’re not here to get a degree in structural engineering, you just need to know this: what you see in your office might be different from what is being used in a cinema hall.
I mean, I’m pretty sure your office doesn’t have such a big duct.
In the meantime, do you know that the Nex incident has also made it to a US website, Variety?
The authorities are still investigating the incident while the cinema remained closed.