There's a strange smell surrounded by my house...? A few days ago, I noticed that one room on the east...

A few days ago, I noticed that one room on the east side of the house smelled unpleasantly. Over the subsequent few days, the smell grew stronger and stronger. It's the only room within the house with that odor and it's be thoroughly vacuumed and dusted and every corner has be inspected. There's no sign of any dead animal or rotten boards or anything. Any design on what it could be, how to find it, and how to deal near it?
Answers:    Your problem is probably not a dead animal, unless it's the size of a house cat or bigger. When mice or even rats die where on earth they are undisturbed, they usually will dehydrate until that time the smell could penetrate the walls.
You probably enjoy one of two problems:
1. Animal droppings- Bats live in walls and swing out in equal general nouns, so there poop builds up over time. Bat guano have a certain smell to it, the best course to describe it is "OLD", like what an aged musty house might smell like. It is toxic if it builds up over years. Bat droppings will smell worse when they are heated, any by the sun beating on the wall or by warmth pipes or hot air ducts. Solution= Best to own an experienced person operate with bat droppings, try ServiceMaster or a pest control company.
2. Plumbing vent stack- your drains are connected to a pipe that runs up inside of a wall and through the roof. This is to equalize pressure so your drains flow other, and also for noxious sewer gases [very poisonous and can be explosive within high concentrations] to escape through a innate draft action, much similar to a smoke stack. In the cold months, sometimes the top of the pipe that sticks above the roof can build up frost inside it, [the warm moist nouns hits the dry bitter cold and condenses like a can of cold soda contained by the summertime, only on the inside of the pipe, which freezes, choking or even seal up the pipe so the gas can't escape. This backup can find its way into your room through poorly hermetically sealed pipe joints or create pressure ample to push past the traps below your sinks. Only solution is call an actual plumber to remedy this.
can you describe the room and out side the glass or whatever from that room?