When you have older carpet that has been spilled on over the years, you may find yourself embarrassed about its smell. If the smell becomes too strong to handle, you need to find an effective way to get rid of the odor without damaging the carpet. Many commercial carpet cleaners are too high priced, however, and contain a large chemical content--which makes it important to use mild ingredients that are effective without the use of chemicals.
Sprinkle a light coat of baking soda over the entire carpet, and let it sit for at least 2 hours, or overnight if possible.
Vacuum the carpet to collect all of the powdery baking soda, which should have absorbed much of the odor along with any moisture that causes a mildew smell.
Fill a spray bottle with white vinegar and lightly mist the carpet. The vinegar odor will dissipate after an hour or so, and will help remove most, if not all, remaining carpet odor.
Steam clean the carpet if the baking soda and vinegar are not effective enough. Pour 2 tsp. laundry detergent and 1 cup white vinegar into the fluid reservoir of the steam cleaner. Top off by adding hot water to the reservoir until you reach the fill line.
Turn on the steam cleaner, and gently run it across the smelly carpet. Move slowly, as the longer the steam has to penetrate the carpeting, the more effective it will be in removing the odor.
Let the carpet air dry for about an hour, and repeat the steam cleaner process if any smell remains on your carpeting.