Okkur ber að athuga öryggisbúnaðinn.

Because this sentence uses an impersonal obligation construction: e-m ber að + infinitive.

In that pattern, the person who has the duty is put in the dative case, not the nominative. So:

• við = we as a nominative subject
• okkur = us in the dative/accusative form

Here, okkur means something like for us / on us / it falls to us.

So the structure is not literally we check..., but more like:

• It is incumbent on us to check...
• We are obliged to check...

That is why okkur is correct here.

Here ber comes from the verb bera, which usually means to carry or to bear.

But in this expression, bera að has a special meaning:

• e-m ber að gera eitthvað = someone is supposed/obliged to do something
• more formally: it is someone’s duty to do something

So in this sentence, ber does not mean carries in the everyday physical sense. It is part of a fixed grammatical expression of duty or obligation.

Because okkur ber að... is an impersonal construction.

Even though okkur refers to us, it is not the grammatical nominative subject in the usual way. The verb stays in the 3rd person singular form:

• mér ber að... = I ought to...
• þér ber að... = you ought to...
• okkur ber að... = we ought to...

So the verb does not change to match okkur as if it were an ordinary subject.

Because after ber in this construction, Icelandic uses að + infinitive.

So:

• ber að athuga = ought to check
• ber að gera = ought to do
• ber að fara = ought to go

The að here is the infinitive marker, similar to English to in to check.

This is worth noticing because not all Icelandic verb combinations use að before an infinitive. But bera að does.

Because athuga is the infinitive.

The only finite, conjugated verb in the sentence is ber. After that, the action itself is expressed with að + infinitive:

• ber að athuga = is obliged to check

If you used athugum, that would be a finite we check / let’s check type form, which does not fit this structure.

So the grammar is:

• okkur = dative person concerned
• ber = finite verb
• að athuga = infinitive phrase

Öryggisbúnaðinn is accusative singular definite.

Why accusative? Because it is the direct object of athuga:

• athuga eitthvað = to check something

Why -inn? Because the noun is definite, meaning the safety equipment, not just safety equipment in general.

Breaking it down:

• öryggisbúnaður = safety equipment
• öryggisbúnað = accusative singular
• öryggisbúnaðinn = accusative singular with the definite article = the safety equipment

So the ending tells you both the case and the definiteness.

It is a compound noun, which is very common in Icelandic.

It is built from:

• öryggi = safety
• öryggis- = the compound form, with a linking -s
• búnaður = equipment

So:

• öryggisbúnaður = safety equipment

In the sentence, the form is öryggisbúnaðinn, because the noun is in the accusative definite singular.

A learner may find this long word intimidating, but it is really just:

safety + equipment + the

packed into one Icelandic word.

Yes, but it sounds more formal, official, or duty-based than some other ways of expressing obligation.

Compare:

• Okkur ber að athuga öryggisbúnaðinn.
  = We are obliged / It is our duty to check the safety equipment.

• Við verðum að athuga öryggisbúnaðinn.
  = We have to / must check the safety equipment.

• Við eigum að athuga öryggisbúnaðinn.
  = We should / are supposed to check the safety equipment.

So okkur ber að... often feels a bit more formal, institutional, or rule-like.

Yes, Icelandic word order is fairly flexible, but Okkur ber að athuga öryggisbúnaðinn is a very natural and standard order.

This sentence starts with okkur, which gives emphasis to us as the ones on whom the duty falls.

You may also see other word orders in different contexts, especially after another element has been placed first. But for a learner, this version is the safest and most natural one to use.

So it is best to learn this pattern as a chunk:

• Mér ber að...
• Þér ber að...
• Honum ber að...
• Okkur ber að...

Not in the same way as in a basic sentence like Við athugum öryggisbúnaðinn.

This is one of those Icelandic expressions where the person involved appears in a non-nominative case instead of as a normal nominative subject. So:

• okkur is the person affected or obligated
• ber is the impersonal verb form
• að athuga öryggisbúnaðinn is the action that ought to be done

For an English speaker, it may help to think of it as something like:

• It falls to us to check the safety equipment
• It is incumbent on us to check the safety equipment

That is why the sentence does not behave like a simple we + verb sentence.