Don't depend on a screen alone to keep children safe. Window guards screw into the side of a window frame and have bars no more than 4 inches apart. They are sold in different sizes for various size windows and adjust for width. Guards must meet requirements for spacing and strength and those that allow for escape in case of emergencies must be difficult for very young children to open. Consumers can also purchase window stops which can be added to the window frame to prevent the window from opening more than 4 inches.
Some new windows come with window stops already installed.
Guards should be installed in children's bedrooms, parents' bedroom, and other rooms where young children spend time. Or, install window stops that permit windows to open no more than 4 inches. Never depend on screens to keep children from falling out of windows. Whenever possible, open windows from the top - not the bottom. Keep furniture away from windows, to discourage children from climbing near windows.