I have never cleaned my Duets, but before I threw them away, I would certainly give it a try with one.

First I would vacuum the blind in place using the round brush attachment of the vacuum cleaner. The more stuff you can get off dry, the further ahead you are.

Then while it is still on the window, I would open it, remove it from the window and gently lay it in the bathtub with some warm water and cleaner of some type. I tend to use liquid Mr. Clean, but maybe something like Dawn dishwashing liquid? Then swish back and forth and repeat with frest water. Using a hand held shower head - or garden house outside - I would rinse it and then hang it somewhere to dry.

All that said, Duets feel like paper to me, so the soap and water and hanging wet could likely destroy the blind.

I used to send mine out. I live in NW suburbs of Chicago. Just call a blind cleaning service. They are in the phone book. Just be sure that they don't pull up in a van and not have the Duets fully opened. That is what they do in the van. This place would come in and take them down around 7 in the morning and come back and rehang them 12 hours later. This place would take them back to their shop and clean them. All of the blind cleaning places use Ultrasonic, much like those denture cleaners. They may use some type of cleaning solution but have never asked. Think it's great that you can wash all of the wood work and windows with nothing in the way. I had not used them in years as I had drapes and sheers in every room. I moved last Oct. and they cleaned all of my mini-blinds in this place. I was not certain that they would still be in business after 16 years. I just pulled the card they gave me when they were here and they have a web-site. I have not been on it but they may explain it better than I have. www.mrslats.com Thank God I looked at the card as I thought they were called Slatz! LOL If you are able to find someone in your area and they R not 2 much $ I would just have them cleaned. If they are dry rotted, forget it. Good Luck.

I have had my blinds cleaned twice just like etienne said above. About 3 years ago, I called a local blind/drapery store to see if they could 'restring' a few blinds since the interior string had broken and I could no longer get the blinds to go up and down. The people at the store were very nice and helpful, and I asked them if they also cleaned blinds. They told me I could do it at home myself. I have Duet pleated shades as well. What they told me to do was to take down the blind. Fill the bathtub halfway with warm water, some detergent like Dawn, and 2 cups of bleach. Put the blind in, one blind at a time, and open it up. Allow the blind to soak for about 20 minutes, then swish it around, gently squeezing and pressing on the fabric. You won't believe how much dirt comes out. Drain the tub and fill it again to cover the blind. Squeeze the fabric to get out the bleach and the soap. Drain the tub again. Leave the blind in the tub and do a final rinse using the shower head, and cold water. Afterwards, squeeze the fabric to remove as much water as possible. Use some big towels to help remove water. Place outside, fully extended to dry (on some towels to prevent dirt. Alternately, you could put the blinds on a clothing line extended, if you have one.
This really works, but it's a bit time consuming. The bleach did not damage the color of my blinds, which are a light yellow. The people at the store told me the fabric was polyester, which would not be damaged by the bleach.

I also cleaned mine in the bathtub. I filled it 2/3 full so I could cover all but the top of the blind in water. I used Dawn dish soap and some oxy clean. I only had them in the water for maybe 5 minutes and was careful not to get the header wet. I then drained the tub refilled it and rinsed with cool water. Finally I used the hand held shower to rinse them one more time. I opened them up and laid them out on towels to dry. Once they were mostly dry I rehung them on the window and left them down to final dry. While not perfect, they are much cleaner and it did not damage them at all.