protect computer from dust

That's the problem with an optical drive in the computer, the opening acts as an intake for the cooling air being pushed out the back by the fan. Of course this mostly happens when the computer is actually in use. I don't know there's much you can do other than when you drive finally dies go for an external drive instead.

or switch internal drives

u still need an internal drive to use an external drive if u dont want to use a bios or kernal of some sort

Storm89161--

Your post is nonsense.

I am not sure what you were trying to say, but the Mac can boot from ANY appropriate drive, Internal or External, and can read DVDs from any drive, Internal or External. You do not need to modify ANYTHING to do this.

Maybe you are thinking of that OS from Redmond, Washington.

You said

So I want to protect my computer at night when it is in sleep mode.

I put/hang a plastic bag over the front and it is kept in place by putting a book on the "handle".

There is some space between the front of the computer and the plastic: 5-7 cm (2-3 inches).

Is that enough for the air to circulate? I remove it when I use the computer. This is only at night.*

That should be fine. However, with the 2- inches I do not think it will it will have any measurable effect on dust accumulation.

I agree with lllaass that the amount of air moved during sleep, and the amount of dust inhaled with it are both nearly negligible.

I think you are most likely to "protect" your Mac from the cooling air it needs, and may cause it to overheat and malfunction.

It is considered routine maintenance to move your Mac Pro silver tower to a place where dust is a "don't care" and use a stream of compressed air to launch the dust airborne and out of your Mac. In most cases, annually is not at all excessive. In your case, perhaps you need to do it a bit more frequently.

Do not allow the plastic tools for a household vacuum cleaner to come anywhere near your Mac. These tools can generate electronics-killing static long before you fell the Zap of a static discharge.

It is probably enough space when asleep and it is not producing that much heat, but I don't think it will make a difference as far as stopping dust from getting inside. If the fans are not running then there is no air draw and the only thing you are protecting is is dust settling on the top of the case. When you do have significant air draw is during the day and that is when you do not want any covers preventing your computer from getting proper cooling.

Get a can of compressed air and once or twice a year take the computer outside (or you will regret this), open it up and blow out accumulated dust. My inclination is to not get too close with the air because it comes out pretty cold and I am worried about suddenly freezing a chip. I live in a house where dust accumulates on things noticeably within a week and that's how I do it with my computer which runs 24/7.

I guess one thing you could try would be to place some kind of cover or foam over the actual optical drive door unless you use it 5 times a day. I don't think it is part of the intentional airflow cooling design and it might reduce intake directly into the drive.