Sense of Smell
Airflow through the nose is actually fast (250ml/sec) and fairly turbulent. Because of this, only a small fraction of the air we breathe is able to pass over the olfactory bulb, the area of the nose responsible for smell.
When we breathe deeply, or sniff, the speed of the air in the nostrils increases, and more of the air comes in contact with the olfactory epithelium.
During a cold the amount of mucus produced increases. This may block the narrow openings to the olfactory tissue, making it more difficult to smell. Think about when you have a cold and can’t smell, often this can affect appetite as loss of smell can put you off eating.
If you are interested, do an internet search on human smell, you will be amazed at what you find!
Click here to search Google.