Fireplace Smokeguard. A fireplace should provide a home with beauty, comfort and enjoyment. The width and height of the fireplace opening, as well as the size of the chimney"s flue, are of utmost importance to its operation. The SmokeGuard works by reducing the fireplace opening and keeping smoke rising up the chimney instead of rolling out into your home. Spring loaded tension bar for easy, secure installation. Heat resistant adhesive caulk (included) seals SmokeGuard in position. Adjusts from 28.5" to 48". Assembly Required. Dimensions: 48" L x 6" W x 1.5" H; 6 lbs.