Humidity is an important factor in many plant propagation systems. Some cloning systems come with humidity domes. A humidity dome is a small imitation of a green house. The humidity dome keeps the humidity high in the area it covers. To keep your humidity dome working properly, spray fine mists on the walls of the dome. You can also use digital timers and water pumps to automate sprinklers to spray the mists for you.
You can create single plant or large humidity domes at home. I used a Chinese food carryout container to make an extra humidity dome.
Use a drill to put a small hole in the container. The hole will let the container get a little air flow while keeping the humidity up. The small hole will also help to prevent the temperature from rising in your humidity dome. Mist the sides of the container with small water drops. Put the container over your plant or clone to put it in a high humidity environment. Fresh cuttings like to be in an environment with 90-100% humidity. Some thermometers have humidity measurements on them. A humidity thermometer is called a humidity hygrometer. Technically humidity meter is incorrect for the situation you will be using the tool. Use home made humidity domes from house hold items to stay economical and green!