The problem that confronts us is this, signor. The atmosphere on Venus is such that a human being cannot breathe and survive for long, even after using what we considered foolproof respiratory equipment.

11 seconds sound clip from the 20 Million Miles to Earth (1957) movie soundboard.

You can hear this line at 00:30:02.493 in the Blu-ray version of the movie.

Quote context

[...]

- I must beg you, however, for the moment, to observe strict secrecy.

- It is understood.

- What I have to say you will find incredible, but true.

- Colonel Calder here has just returned from an expedition to Venus.

- To Venice. Perhaps you mean Venezia.

- To Venus. The planet Venus.

- The planet Venus?

- That is correct.

- I was informed this matter was connected with something vast, but the the planet Venus?

- Man's first interplanetary voyage. On the return trip, the spaceship was crippled by a meteor. Except for colonel Calder here, the entire crew perished.

- I am grieved.

- The problem that confronts us is this, signor. The atmosphere on Venus is such that a human being cannot breathe and survive for long, even after using what we considered foolproof respiratory equipment.

- Several members of the expedition died there before the others realized the danger.

- And Doctor Sharman, the chief scientist, also became fatally ill.

- He died here after the ship crashed.

- Fascinating. Horrible, but fascinating.

[...]