Chất thải nguy hại không ở trong túi rác.

A natural word-by-word breakdown is:

• chất thải = waste
• nguy hại = hazardous, dangerous
• không = not
• ở trong = to be in, to be inside
• túi rác = trash bag, garbage bag

So the structure is basically:

• Chất thải nguy hại = hazardous waste
• không ở trong = is not in
• túi rác = the trash bag / a trash bag

Because in Vietnamese, descriptive words usually come after the noun, not before it.

So:

• chất thải nguy hại = hazardous waste
• literally: waste hazardous

This is very normal in Vietnamese. English speakers often want to put the adjective first, but Vietnamese usually does the opposite.

Compare:

• nhà lớn = big house
• xe mới = new car
• chất thải nguy hại = hazardous waste

In Vietnamese, không usually goes before the verb or predicate to make it negative.

Here, the predicate is ở trong = to be in / to be located inside.

So:

• ở trong túi rác = is in the trash bag
• không ở trong túi rác = is not in the trash bag

This is the normal negation pattern:

• Tôi hiểu. = I understand.

• Tôi không hiểu. = I do not understand.

• Nó ở đây. = It is here.
• Nó không ở đây. = It is not here.

Yes, in this sentence ở works like a location verb meaning to be located at/in.

Vietnamese does not use one single word exactly like English to be in every situation.

For location, Vietnamese often uses ở:

• Tôi ở nhà. = I am at home.
• Cuốn sách ở trên bàn. = The book is on the table.
• Chất thải nguy hại không ở trong túi rác. = Hazardous waste is not in the trash bag.

So ở is not a general all-purpose to be, but in location sentences it fills that role.

Trong by itself means in / inside, but ở trong is the more complete and natural form when you are saying something is located inside something.

• trong túi rác = in the trash bag
• ở trong túi rác = is in / is located inside the trash bag

In a full sentence, ở trong often sounds clearer and more standard:

• Nó ở trong hộp. = It is in the box.

If you remove ở, the sentence may sound incomplete or less natural in standard usage.

Vietnamese usually does not mark articles or plural the way English does.

So túi rác can mean:

• a trash bag
• the trash bag
• trash bags in a general sense, depending on context

And chất thải nguy hại can mean:

• hazardous waste
• the hazardous waste
• hazardous wastes

Context tells you how specific or general it is.

If Vietnamese needs to be more specific, it can add other words, for example:

• một túi rác = a trash bag
• túi rác này = this trash bag
• các túi rác = trash bags

Túi rác means trash bag / garbage bag.

If you mean trash can / garbage bin, you would usually say:

• thùng rác = trash can / garbage bin
• sometimes sọt rác = wastebasket / trash bin

So this sentence specifically talks about a bag, not a bin.

That distinction matters:

• trong túi rác = in the trash bag
• trong thùng rác = in the trash can

It is best understood as a mass/general noun, like English waste.

So it does not strongly feel singular or plural by itself. It refers to the category or substance in general.

That is why:

• Chất thải nguy hại = hazardous waste

If you wanted to refer to a specific piece or type, you would add more detail, for example:

• loại chất thải nguy hại này = this type of hazardous waste
• những chất thải nguy hại đó = those hazardous wastes

But in your sentence, it is generic: hazardous waste.

Literally, it is a statement of location:

• Chất thải nguy hại không ở trong túi rác.
• Hazardous waste is not in the trash bag.

However, if your intended meaning is more like a rule or warning such as Hazardous waste does not go in the trash bag or Do not put hazardous waste in the trash bag, Vietnamese more naturally says something like:

• Không bỏ chất thải nguy hại vào túi rác. = Do not put hazardous waste in the trash bag.
• Chất thải nguy hại không được bỏ vào túi rác. = Hazardous waste must not be put in the trash bag.

So your original sentence is grammatical, but for signs or instructions, a different wording is often more natural.

Chất thải nguy hại is the standard and very common term for hazardous waste, especially in formal, technical, environmental, or legal contexts.

Chất thải độc hại can sometimes be understood, but it is not exactly the same in meaning:

• nguy hại = hazardous, dangerous in a broader sense
• độc hại = toxic, poisonous, harmful

So độc hại focuses more on toxicity, while nguy hại is broader and better matches English hazardous.

That is why chất thải nguy hại is usually the safer choice for hazardous waste.

A careful pronunciation guide would be something like:

• Chất thải nguy hại không ở trong túi rác

A rough English-friendly approximation:

• chut thai nwee hai khong uh trong too-ee rak

A few important notes:

• chất has a short, clipped ending
• thải has a falling/rising tone shape depending on dialect
• nguy is one syllable that may feel unusual to English speakers
• ở has a vowel sound that does not exist exactly in English
• túi is two vowel sounds close together
• rác has a sharp final consonant

If you are learning pronunciation, it helps to practice it in chunks:

• chất thải nguy hại
• không ở trong
• túi rác