# 'How long does it take CO2 would go away?' Grammatically right?

'How long does it take CO2 would go away?' : This is the sentence. For me, this sounds strange.

I have thought in many different ways, but I can not find one possible explanation. One of my coworkers said that there is 'elliptical that' before 'CO2', but it sounds even more wrong.

Then, the statement sentence of this will be like :

'(That)CO2 would go away takes ~~~ years.'

Is this a right sentence?? I don't think so.

So, I'd like to know if this sentence is grammatically right,first.

If it is, I would have many studies to do, and probably lots of questions to ask, too. :)

Thank you~!

• "How long does it take for CO2</sub> to dissipate?" "The CO2 will (have dissipated)(dissipate) in N years." Jul 5, 2016 at 2:37

How long does it take for CO2 to go away?

It takes ~ years.

This uses present simple tense and represents factual information. It sounds like this is a natural occurrence.

A: We can do X, Y and Z to help the process.

B: How long would it take for the CO2 to go away?

A: It would take ~ years.

This uses would for a conditional question. In this example person A offers a solution and person B asks, given that situation, how long would it take?

On a side note "CO2 to go away" seems somewhat ambiguous.

Edit: @Cardinal asked: What about "How long would CO2 take to go away" ? or "How long CO2 would take to go away"

"How long would CO2 take to go away?" seems grammatically sound to me but has a different meaning. In this case, the condition is that CO2 is used instead of something else.

A: If we use this process it takes nitrogen 2 hours to go away.

B: How long would CO2 take to go away?

A: It would take 4 hours.

@VCCine

• Thank you for your answer. I know what you mean. The functions of present simple tense, and of the modal verb. Considering this, the question sentence seems strange. Jul 5, 2016 at 2:57
• How about 'How long would it take that CO2 would go away?'? Will it be OK to say like this? Thank you Jul 5, 2016 at 3:33
• No, that isn't correct either. What do you find unacceptable with the example sentence that I have given you? Please give more context as to what you are trying to say.
– Leo
Jul 5, 2016 at 3:51
• @Leo What about "How long would CO2 take to go away" ? or "How long CO2 would take to go away" Jul 5, 2016 at 3:58
• @Leo No,no, I didn't mean that 'your sentence' is not right. I meant 'my question sentence'. :) Yours looks just right to me. Thank you. :) My biggest question is if you use 'that-clause' in such questions, without using to-infinitive. I know 'How long does it take FOR CO2 TO go away?' is ok, but not sure about 'How long does it take THAT CO2 would go away?' Very... simple and not very valuable question it is, but for non-native speaker like me, sometimes this kind of questions matters. :) Jul 5, 2016 at 4:22

'How long does it take CO2 would go away?' : This is the sentence. For me, this sounds strange.

Infinitives that are the "object", complement, predicate, etc. of a verb cannot take modals. Modals need a verb that has a subject.

A simpler example:

I want to walk to the park.

You cannot do any of this:

I want to would walk to the park.

I want to do walk to the park.

You have to attach modals to the actual verb in the sentence only, the one that has a subject.

I would want to walk to the park.

I do want to walk to the park.

Also the words would, should, could, must, and shall "override" the required do in questions.

So you have to say this:

How long would it take CO2 to go away?