Why do basement car parks in Bangkok tower blocks always stink to high hell?

[short-Timer]

I won’t name building names, but every time I step into one of these underground car parks in Bangkok, there’s this foul stench I just can’t quite explain. Poor airflow doesn’t help, obviously, and years of engine fluids soaking into the concrete seem to have brewed up some kind of chemical horror. It’s always mixed with that signature whiff of stale, stagnant Bangkok air, the same one that smacks you in the face when you start heading down the steps into the MRT. I don’t know exactly what’s in that car park cocktail. Maybe some sewage gases thrown in for good measure? Whatever it is, it’s absolutely rank. I’m honestly surprised the security staff working underground in those buildings, breathing all those exhaust fumes, don’t just gag and pass out. After just a few minutes in one of those places, I feel like I’m suffocating. The air must be heavy with carbon monoxide and carbon dioxide and practically starved of oxygen.

Grok said this:

 

The foul stench in Bangkok’s underground car parks is a grim mix of environmental and infrastructural issues, intensified by the city’s unique conditions. Here’s a breakdown of what’s likely causing it and why it feels so suffocating:

 

Trapped Vehicle Emissions and Fluids: Poor ventilation in these car parks means exhaust fumes—carbon monoxide, nitrogen oxides, and particulate matter—linger. Leaked engine fluids like oil, gasoline, and coolant seep into the porous concrete, breaking down and releasing volatile organic compounds (VOCs) over time. These mix with tire dust and create a persistent chemical stink that’s baked in by Bangkok’s heat.

Tropical Humidity and Organic Decay: Bangkok’s humid, tropical climate is a breeding ground for mold, mildew, and bacteria, especially in poorly ventilated underground spaces. Stagnant air traps moisture, which encourages microbial growth on surfaces or in drains. Add in organic matter—food waste, dead rodents, or even plant debris swept in from the street—and you’ve got decomposition adding to the stench. This is likely the “stale Bangkok air” you notice, also present at MRT entrances.

 

Sewage and Drainage Issues: Sewage gases, like hydrogen sulfide (that rotten egg smell), could be leaking from aging or poorly maintained drainage systems. Bangkok’s underground infrastructure, especially in older buildings, often struggles with clogged or inadequate drains, letting gases seep into car parks. Flooding, common in the city, can also back up sewers, worsening the problem.

Unique Urban Cocktail: The “signature” underground smell you describe—unlike anything in other countries—might come from this blend of vehicle pollutants, tropical decay, and urban grit, intensified by Bangkok’s dense traffic and aging infrastructure. The city’s chaotic mix of street food, open drains, and constant construction adds particulate matter and odors that settle into enclosed spaces.

Air Quality and Health Concerns: The suffocating feeling and worry about security staff are spot-on. Underground car parks with poor airflow can have elevated carbon dioxide (CO2) levels from trapped vehicle exhaust, reducing oxygen availability. Carbon monoxide (CO) and VOCs further degrade air quality, causing dizziness, nausea, or respiratory irritation. Long-term exposure for workers is a real health risk—studies on similar environments show increased rates of respiratory issues and fatigue. Bangkok’s car parks often lack proper mechanical ventilation systems, and natural airflow is near nonexistent underground, so pollutants just build up. The heat and humidity make it feel even more oppressive, amplifying the sense of suffocation.

 

Why It’s Worse in Bangkok: Compared to other countries, Bangkok’s combination of high humidity, dense urban pollution, and often outdated building systems creates a perfect storm. Many developed countries enforce stricter ventilation standards or use sealed concrete coatings to prevent fluid absorption, which Bangkok’s older buildings often lack. The city’s tropical setting also means odors don’t dissipate as they might in drier or cooler climates.

 

If you’re feeling overwhelmed after a few minutes, it’s likely the combo of low oxygen, high CO2, and irritants like VOCs and particulate matter hitting your system. Security staff might build tolerance or just have no choice but to endure it, but it’s definitely not healthy. Some buildings might skimp on maintenance to cut costs, neglecting air filters or exhaust systems, which makes things worse.

[scubascuba3]

My Pattaya condo 20+ floors basement smells fresh and breezy, that's because wind blows off the sea and through the car park

[SAFETY FIRST]

1 hour ago, short-Timer said:

Why do basement car parks in Bangkok tower blocks always stink to high hell? 

Poor ventilation 

 

You live in Bangkok and complain about air quality, come on, give me a break 

[short-Timer]

1 hour ago, scubascuba3 said:

My Pattaya condo 20+ floors basement smells fresh and breezy, that's because wind blows off the sea and through the car park

I think it’s a smell that’s unique to Bangkok. Back when they were doing all the tunnel excavation, more than 20 years ago, when they built Rama 4 section of the MRT, I spent quite a bit of time walking through those concrete tunnels, and it was the same stench I’m talking about now, minus, of course, the added stink from car fumes you get in the basement car parks. But down in those tunnels, it had that same rank, Bangkok underground stagnant smell. If you ever smelled it then it’s something you would never forget. And I still catch a whiff of it every time I start walking down the stairs into the MRT system, even now. I figured the smell in the MRT might fade after the first decade or so, but it never seems to go away. However, the basement car park smell is even worse.

[scubascuba3]

36 minutes ago, short-Timer said:

I think it’s a smell that’s unique to Bangkok. Back when they were doing all the tunnel excavation, more than 20 years ago, when they built Rama 4 section of the MRT, I spent quite a bit of time walking through those concrete tunnels, and it was the same stench I’m talking about now, minus, of course, the added stink from car fumes you get in the basement car parks. But down in those tunnels, it had that same rank, Bangkok underground stagnant smell. If you ever smelled it then it’s something you would never forget. And I still catch a whiff of it every time I start walking down the stairs into the MRT system, even now. I figured the smell in the MRT might fade after the first decade or so, but it never seems to go away. However, the basement car park smell is even worse.

Probably many fatbergs in the sewers partially blocking everything

[short-Timer]

13 minutes ago, scubascuba3 said:

Probably many fatbergs in the sewers partially blocking everything

Sounds like something they could use to make fancy soap from and then sell it back to the rich people, like in Fight Club. 

[Kinnock]

Thai drains and plumbing almost never have proper water seals.  No bends in the pipe to create a trap, drain covers with just 1mm of water seal that evaporates within minutes.  So the drains are open to the sewers and all the sewer gasses enter the lower building levels.

 

Add in all the cross connections of foul drains into the rainwater systems, plus all the cooking fat tipped into the street drains, and you get that classic Bangkok stink.

 

Then when it rains, the foul air is pushed out of the drains and into the car parks and lower building levels.

[Mutt Daeng]

People using it as a pissoir?

[fredwiggy]

In the states, in large cities, it's much the same, with those mentioned reasons, along with vagrants pissing there. Can't forget the smell of apartment buildings in NYC either, just as you walk in past the first door. There it was the pee and mold.

[Showtime]

I'm sorry to hear you don't like the smell of my natural gas.

[Harrisfan]

4 hours ago, SAFETY FIRST said:

Poor ventilation 

 

You live in Bangkok and complain about air quality, come on, give me a break 

Why is he hanging out in carparks?

[sikishrory]

Something to do with dripping sewerage pipes?

My condo and also the mall in Phuket reeks of poos.

If you're hungover it can tip you over the edge.

[crazykopite]

Because Thais will take a leak anywhere they lack dignity I’ve seen it happen many times even witnessed a Thai woman crouching die for all to see

[Will B Good]

Smell better than the ones in the UK, which are used as open urinals.

[Ralf001]

10 hours ago, short-Timer said:

I won’t name building names, but every time I step into one of these underground car parks in Bangkok, there’s this foul stench I just can’t quite explain. Poor airflow doesn’t help, obviously, and years of engine fluids soaking into the concrete seem to have brewed up some kind of chemical horror. It’s always mixed with that signature whiff of stale, stagnant Bangkok air, the same one that smacks you in the face when you start heading down the steps into the MRT. I don’t know exactly what’s in that car park cocktail. Maybe some sewage gases thrown in for good measure? Whatever it is, it’s absolutely rank. I’m honestly surprised the security staff working underground in those buildings, breathing all those exhaust fumes, don’t just gag and pass out. After just a few minutes in one of those places, I feel like I’m suffocating. The air must be heavy with carbon monoxide and carbon dioxide and practically starved of oxygen.

Grok said this:

 

The foul stench in Bangkok’s underground car parks is a grim mix of environmental and infrastructural issues, intensified by the city’s unique conditions. Here’s a breakdown of what’s likely causing it and why it feels so suffocating:

 

Trapped Vehicle Emissions and Fluids: Poor ventilation in these car parks means exhaust fumes—carbon monoxide, nitrogen oxides, and particulate matter—linger. Leaked engine fluids like oil, gasoline, and coolant seep into the porous concrete, breaking down and releasing volatile organic compounds (VOCs) over time. These mix with tire dust and create a persistent chemical stink that’s baked in by Bangkok’s heat.

Tropical Humidity and Organic Decay: Bangkok’s humid, tropical climate is a breeding ground for mold, mildew, and bacteria, especially in poorly ventilated underground spaces. Stagnant air traps moisture, which encourages microbial growth on surfaces or in drains. Add in organic matter—food waste, dead rodents, or even plant debris swept in from the street—and you’ve got decomposition adding to the stench. This is likely the “stale Bangkok air” you notice, also present at MRT entrances.

 

Sewage and Drainage Issues: Sewage gases, like hydrogen sulfide (that rotten egg smell), could be leaking from aging or poorly maintained drainage systems. Bangkok’s underground infrastructure, especially in older buildings, often struggles with clogged or inadequate drains, letting gases seep into car parks. Flooding, common in the city, can also back up sewers, worsening the problem.

Unique Urban Cocktail: The “signature” underground smell you describe—unlike anything in other countries—might come from this blend of vehicle pollutants, tropical decay, and urban grit, intensified by Bangkok’s dense traffic and aging infrastructure. The city’s chaotic mix of street food, open drains, and constant construction adds particulate matter and odors that settle into enclosed spaces.

Air Quality and Health Concerns: The suffocating feeling and worry about security staff are spot-on. Underground car parks with poor airflow can have elevated carbon dioxide (CO2) levels from trapped vehicle exhaust, reducing oxygen availability. Carbon monoxide (CO) and VOCs further degrade air quality, causing dizziness, nausea, or respiratory irritation. Long-term exposure for workers is a real health risk—studies on similar environments show increased rates of respiratory issues and fatigue. Bangkok’s car parks often lack proper mechanical ventilation systems, and natural airflow is near nonexistent underground, so pollutants just build up. The heat and humidity make it feel even more oppressive, amplifying the sense of suffocation.

 

Why It’s Worse in Bangkok: Compared to other countries, Bangkok’s combination of high humidity, dense urban pollution, and often outdated building systems creates a perfect storm. Many developed countries enforce stricter ventilation standards or use sealed concrete coatings to prevent fluid absorption, which Bangkok’s older buildings often lack. The city’s tropical setting also means odors don’t dissipate as they might in drier or cooler climates.

 

If you’re feeling overwhelmed after a few minutes, it’s likely the combo of low oxygen, high CO2, and irritants like VOCs and particulate matter hitting your system. Security staff might build tolerance or just have no choice but to endure it, but it’s definitely not healthy. Some buildings might skimp on maintenance to cut costs, neglecting air filters or exhaust systems, which makes things worse.

You live in Bangkok and complain about air quality, come on, give me a break 

[khunjeff]

11 hours ago, short-Timer said:

that signature whiff of stale, stagnant Bangkok air, the same one that smacks you in the face when you start heading down the steps into the MRT

 

I use the MRT all the time, and no smell of any kind "smacks you in the face" at any station. The system is clean and well ventilated.

[oldestswinger]

Pee always eventually runs downhill.

[Robert Smith 2]

Noseblindness, most Thais suffer from it...

[Photoguy21]

Lack of adequate ventilation

[Thingamabob]

No worse than underground car parks anywhere in any country. A combination of reasons, not the least of which is vagrants using them as a lavatory.

[Patong2021]

Bangkok  elevation ranges from -11m to 3 m with an average elevation of 1.5 m. In contrast the elevations for other large cities are; Paris 35m,  London 11m, Tokyo 40m, Singapore 11m, Chiang Mai 310m, Surat Thani 10m, and Patong 97 m

Bangkok is built on reclaimed swamp. Swamps are known to hold tons upon tons of decaying organic material that has built up over centuries.  No amount of ventilation will remove the gas byproduct of natural decay in a swamp.

 

 

[Briggsy]

The yaam used to pee in the underground car park of my old condo (I miss that old condo). I put up a haam yeeo sign which seemed to work.