Respirators are not the same as surgical masks. Surgical masks do not protect against breathing in very small particles such as dust or mold because they do not fit tightly to the face, allowing air particles to leak in around the edge of the mask.
6. How long did it take to build the Great Wall in China? The Great Wall of China was built in several stages, not in one continuous effort. Beginning is the 6-7th century BC and ending in the 16th century AD. 7. How wide and how tall the Great Wall of China is? The Great Wall is wide enough at the top for five horses or ten men to walk side by side. The Great Wall ranges in height from just a few feet to over 30 feet tall. Since some of the Wall is built on mountain peaks and high ridges, it looks even taller. 8. What is the best time to visit the Great Wall of China?
Updated March 03, 2017. The Great Wall of China is not a continuous wall but is a collection of short walls that often follow the crest of hills on the southern edge of the Mongolian plain. The Great Wall of China, known as long Wall of 10,000 Li in China, extends about 8,850 kilometers (5,500 miles). Building the Great Wall of China A first set of walls, designed to keep Mongol nomads out of China, were built of earth and stones in wood frames during the Qin Dynasty (221-206 BCE). Some additions and modifications were made to these simple walls over the next millennium but the major construction of the modern walls began in the Ming Dynasty (1388-1644 CE).