[Grammar] Is the “when” used as a preposition?

[ben9108]

I would like to seek someone to solve my question about the usage of “When”. Is the “when” used as a preposition and a gerund following it shown below sentences?

Doors to refrigerated spaces should be kept closed when not in use.

What special precautions should be taken when using XYZ medicament.

Protect information when using the internet and email

How might I be putting information at risk when using the internet?

 

[Rover_KE]

I'd say it's an adverb.

 

[Raymott]

I'd add that it's not a gerund or a preposition. Most dictionaries give an accurate listing of the parts of speech that a word can be.

 

[tzfujimino]

I would like to seek someone to solve my question about the usage of “When”. Is the “when” used as a preposition and a gerund following it shown below sentences?

Doors to refrigerated spaces should be kept closed when [they are] not in use.

What special precautions should be taken when [we are] using XYZ medicament.

Protect information when [you are] using the internet and email

How might I be putting information at risk when [I am] using the internet?

Hello.:-D
Those words in square brackets are omitted and therefore the 'when' in this construction is a conjunction.
This is what I teach to my students.