"Put it on", demands my guide María, giving me a gas mask.
Looking at the rest of the group struggling with their masks, I decide that this is probably the best course of action and I get rid of it.
I am 30 feet underground in a top secret Soviet bunker in the heart of Latvia on the centenary of the country's first declaration of independence, and seeing what life was like under Soviet occupation.
Hidden secrets: a uniform guide inside the bunker of the Soviet Union in Ligatne, Latvia, 50 miles from Riga
The hallways of the bunker were painted olive green following the advice of Soviet psychologists.
Tourist attraction: Known by its code name, the Pension, the bunker was completed in 1982
The bunker, which has been recently opened to the public, is accessible only through the back door of the rehabilitation center of the sixties in Ligatne, 80 kilometers from Riga in the Gauja National Park.
Known by its code name, the Pension, the bunker was completed in 1982 and served as one of the strategic hiding places of the USSR, so its whereabouts secret was classified until 2003.
At full capacity, up to 250 workers manned this network of 90 rooms, 2,000 square meters, in preparation for a large-scale nuclear war. From the monolithic radio equipment to the Soviet decoration on the walls of the canteen, not much has changed since then.
Isolated from the outside world with a 15-foot concrete layer, our guide Maria tells us that the bunker is equipped with its own power supply, a well for drinking water and sufficient supplies for three months.
Then he takes us through the labyrinth of olive green corridors, painted with the advice of Soviet psychologists who believed that color promoted well-being.
Our first stop is the communications room, where the KGB agents use a stack of tape reels to record phone calls. In the next room, under a facade of Lenin, there is a desk with a red telephone, which Maria informs us was the Kremlin's direct line.
Chlling: this room has a map, a conference table and a figure marked as "Lenins".
In an adjoining room there is a small bed, the only one in the complex, reserved for Boris Pugo, the interior minister who committed suicide after the collapse of the Soviet Union in 1991.
But the best has been saved to last.
The war room, taken directly from Dr. Strangelove, is filled with maps and tables detailing strategic points of interest. One in particular catches my attention. It is a map of the United Kingdom with my hometown, Reading, marked in Cyrillic, which makes me shudder to think that I may have been a Soviet target.
Alex ate in the canteen during his visit, where they served him watery meatballs with a spoonful of sour cream.
Historical trip: the Ligatne bunker tours cost £ 12, including a meal
A guide reveals the secrets of bunkers to a group of tourists.
The bunker was kept secret until 2003. It's a strange experience to be inside, says Alex.
Above the door there is a flashing red light. I ask what it is for and Maria responds: "Red code: immediate evacuation".
Following our example, we go to the canteen where we get a plate of watery meatballs with a spoonful of sour cream.
I look at all the Soviet propaganda. One of the posters is of a sullen woman with an index finger in her mouth reminding her classmates that their work should remain secret. Today we could not suspect more of Russia and a visit here will do little to reassure you.
You can access the bunker only through the back door of a rehabilitation center of the sixties in the Gauja National Park (in the image)
The visits to the Ligatne bunker cost £ 12, including a meal. For more information visit bunkurs.lv.