Cleaning monitor and scanner. Even some household glass cleaners which you might think could be trusted, can scratch the glass in your monitor or flatbed scanner when used with a rag or paper towel. With a scanner, small scratches can mean real trouble because a scratch can easily show up in your images at higher resolutions. Therefore, you should use only a dry, soft photographer's lens cloth which won't scratch or lens cloths with alcohol that are made specifically for monitors and scanners.
Never spray liquids onto a flatbed scanner. If liquid gets under the glass and into the body of the scanner, you could end up with condensation on the inside of the scanner when you use it. Again, a dry, photographer's lens cloth is a good choice. Or moistened lens cloths, which don't carry enough alcohol to do any harm.
Computer Monitors should never be opened. Never take the cover off any type of monitor, even if it needs cleaning. Why? Your PC's monitor is one of the two components of your system that carry enough voltage to seriously hurt you. If your computer monitor needs to be serviced or cleaned on the inside, take it to your local computer shop.
Use a cover for your scanner. Scanners are somewhat different from most external peripherals. They don't generate any heat while they are on, and most of us only use a scanner once or twice a week. Therefore, your scanner is a perfect candidate for a cover that will keep it clean. And, by no small coincidence, you'll find such covers at your local office supply store.