The short answer to your question is yes- smoke makes the atmosphere thicker. But I should probably explain what I mean by thicker. When large amounts of smoke are released from an event such as a wildfire, it gets stuck in the atmosphere. Smoke is a generic term for a mixture for the gases released when something burns (water vapor, carbon dioxide, etc.) as well as the soot (soot being a solid particle, not a gas). When smoke gets into the atmosphere, it actually absorbs solar radiation and reduces the amount that reaches the earth. The magnitude of this effect depends on how much smoke is in the atmosphere, how black the smoke is, and how high in the atmosphere it is located. So smoke in the atmosphere can actually cool the earth below it. However, smoke is still a form of pollution that can contribute to things like acid rain. So while it is true that smoke makes the atmosphere thicker, scientists are still studying the full effect of smoke and how it contributes to the climate and pollution. Have a great day!