Name: The world's cleanest railway
Uploaded: 2026-01-19T17:29:57.000Z
Duration: 6 min 6 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Since 1967, Cea Leti here in Grenoble in the southeast of France, has been one of the world's largest research hubs for electronics and nanotechnology.

And by the mid 2000s, the folks here had a problem.

Adverbs of manner

They had two clean rooms, two carefully controlled spaces with purified air where research and testing could be done without any dust or contaminants getting in the way.

But those two clean rooms were 250 metres apart on opposite sides of a road where.

Which is the kind of thing that happens when your camper steadily grows over decades.

So every time some tiny component or piece of equipment needed to be moved from one to the other, it had to be put in sterile packaging.

Then the researchers would have to leave the clean room, take off all their gowns and gloves and shoe covers, walk over, put on a whole new set of protective gear, clean off the packaging and then finally go in and unpack it.

They built the world's cleanest people mover, a a clean room on wheels that can somehow dock and undock the main buildings without letting any outside air in.

The cleanroom is about 11,000 square meters.

Today at Lette, we have about 2,000 employees and 800 of them are focusing on fabrication.

We are making devices from components to sensors, and

we are mixing a wide variety of technologies, including lasers, quantum technologies.

We are able to print circuits down to the 10 nanometer.

This is a device that you will find in your phone or in drones and specific systems.

To speak about the dimension, we said that the thickness of one hair is about 50 microns.

So when we discuss a transistor with a dimension of 10 nanometers, it's about 5,000 times smaller than a hair.

And the risk is that when one hair is dropping on the surface, that of course the circuit won't operate.

All of the horrible human stuff is sealed inside many layers.

We have to operate in very clean environment since the source of contamination is us.

So basically we have to wear special clothes to protect the wafers and the dies and the circuits and the nanotransistors from us.

that's a colossal amount of space that would have to be filled with ventilation and air treatment equipment all the way along, all constantly running and maintained at huge expense.

Also, they were worried about how people would feel walking down an isolated, empty, narrow, sealed in 250 metre corridor with no doors where you can't see the other end because it needs steps in the middle to get over the road.

I would say compared to the hospital and the surgical theater.

The surgical theater has probably 100 times more particles in the air.

And I would say that the house has probably 1 million times more particles in the air.

We can see these big gray pipes, and this is the way that we are operating.

The recirculation of the air from the top to the basement through the clean rooms.

I should point out there's three or four people crowded behind the camera here.

I'm not being allowed in the clean room funicular on my own.

The air is still being circulated just as it was in each of the buildings.

The concrete supports that we're traveling over and all the powered systems that are hauling the cables that are moving us are.

they are about as standard as you can get for something like this.

They're manufactured by a company called Poma, who make all sorts of ropeways.

But this clean room that sits on the top, well, making this work was up to the folks in the cea.

So in the cleanroom, we have a special team which take care of the cleaning of the surfaces and make sure that no particles are stuck.

So the cleaning team is also operating within the shuttle.

The problem is that this has to dock and undock from the clean rooms.

How does dust and outside air not get inside?

The cabin slows down a lot at the end of its run.

And that's because it has to position itself extremely carefully, millimetre accurate, to make sure the rubber seal on this door matches up with the rubber seal on the door of the cleanroom.

They get connected, and then high pressure air blasts out anything in between.

All the outside atmosphere is exhausted by fresh, clean air.

And this whole system, the people mover and the clean room, is kept at a slightly higher pressure than the outside.

So if there ever is a leak, it's only going to leak outwards.

When you enter the shuttle, the door will close.

And then you have to wait for maybe 30 seconds before there is a higher pressure inside.

And then at the end, we have the same operation.

It's to demonstrate depressurize the shuttle to allow the door to open and the operator to move in the next cleanroom facility.

So why not just let people keep walking over the old fashioned way.

Well, before this was installed, the researchers here estimated that transporting stuff between the two rooms was so inefficient that it lost the time equivalent of seven or eight full time jobs.

And rebuilding the clean rooms would cost far, far more.

This might seem a bit unnecessary at first, but out of everything, probably the least expensive option.

I can't do the walk off into the distance.