При переохлаждении нужно спасательное одеяло.

Because при normally takes the prepositional case when it means in/under conditions of.

So:

• base form: переохлаждение
• after при: при переохлаждении

This whole phrase means something like in case of hypothermia or when there is hypothermia.

Here при does not mean a physical location like at.

In this sentence, при means something like:

• in case of
• in the event of
• under conditions of
• when there is

So при переохлаждении is a common medical/instructional way to say in cases of hypothermia.

Переохлаждение is a neuter noun ending in -ие. Nouns of this type usually have -ии in the prepositional singular.

For example:

• здание → в здании
• состояние → в состоянии
• переохлаждение → при переохлаждении

So this is a regular pattern.

Because одеяло is a neuter singular noun, and the short form of нужный agrees with it:

• нужен for masculine singular
• нужна for feminine singular
• нужно for neuter singular
• нужны for plural

Compare:

• Нужен врач.
• Нужна вода.
• Нужно одеяло.
• Нужны перчатки.

So нужно спасательное одеяло = a rescue blanket is needed.

It looks the same, and that can be confusing.

In this sentence, the easiest way to understand it is as the short-form adjective agreeing with одеяло:

• спасательное одеяло нужно

That is why it matches the neuter singular noun.

Russian learners often first meet нужно in sentences like:

• Нужно идти. = It is necessary to go.

That is a different but related use. In your sentence, think of it as needed rather than just necessary.

Because the sentence is built like X is needed, not someone needs X.

So спасательное одеяло is the thing that is needed, and it stands in the nominative:

• Спасательное одеяло нужно.

If you explicitly say someone needs it, Russian often uses a dative person plus a nominative noun:

• Пострадавшему нужно спасательное одеяло.
  = The injured person needs a rescue blanket.

So this is not a normal direct-object accusative structure.

Спасательное comes from спасать = to save / rescue.

In this context, спасательное одеяло means a rescue blanket, emergency blanket, or survival blanket. It is the standard adjective used for equipment meant for rescue or emergency situations.

So it does not mean a blanket that is actively rescuing someone in a grammatical sense; it means a blanket used for rescue/emergency purposes.

Yes. Russian word order is flexible.

This sentence begins with При переохлаждении to set the situation first:

• При переохлаждении нужно спасательное одеяло.

You could also say:

• Спасательное одеяло нужно при переохлаждении.

Both are understandable. The original order sounds natural in instructions, medical advice, and safety guidelines because it starts with the condition first.

Russian has no articles.

So спасательное одеяло can mean:

• a rescue blanket
• the rescue blanket

The exact sense depends on context. In a general instruction like this, English usually uses a:

• A rescue blanket is needed.

Not always with perfect one-to-one precision.

Переохлаждение often refers to overcooling of the body and can correspond to hypothermia in many contexts, especially medical or first-aid ones. In everyday Russian, it can sometimes be a bit broader than a strict technical diagnosis.

So in a first-aid sentence like this, hypothermia is a very natural translation.

The main stresses are:

• при переохлажде́нии
• ну́жно
• спаса́тельное
• одея́ло

So a natural pronunciation is:

При переохлажде́нии ну́жно спаса́тельное одея́ло.