Applying a sealer or topcoat after staining wood is highly recommended, though not always strictly required. A sealer protects the wood from moisture, UV rays, and weather-related issues, which is especially important for outdoor surfaces like decks and fences. It also enhances the stain's durability, prevents fading over time, and gives the wood a cleaner, more professional-looking finish. For some indoor applications, a sealer may not be necessary, depending on the type of stain used and the level of protection needed. It's always best to check the stain manufacturer's recommendations and consider the wood's intended use and exposure when deciding whether to apply a sealer.

Whether to paint or stain a deck depends on your personal preference for appearance and budget. Stain provides a natural look with a range of undertones, is typically less expensive, and may only require one coat, but it does not last as long as paint. Paint offers a sleeker finish with a virtually unlimited color palette. Both options will protect your deck from outdoor elements like rain, snow, and general wear and tear.

When choosing between deck stain or paint, knowing what will last longer is important. Deck paint lasts longer than deck stain. With deck paint, you can get up to 10 years of coverage before you need to reapply. With deck stain, that time is significantly shorter at two to three years. 

Wood stain is not flammable after it dries. The solvent in wood stain is what causes the liquid form to be highly flammable, but the stain drying process involves the solvents dissolving, which leaves behind a non-flammable product on your wood project. Wood stain is, however, flammable before you apply it, so you should always store partially full cans and used wood stain rags away from sources of heat and open flames.