Why felt is used for thermal insulation in preference to air?

Thermal conductivity of air is less than that of felt but felt is a better heat insulator in comparison to air. Why ?

Thermal conductivity of air is less than of felt but is a better heat insulator in comparison to air why?

Is air an insulator?

Answer the following Why is a mixture of helium and oxygen gas preferred over air for respiration during deep sea diving?

Name the acid used for the preparation of hydrogen chloride gas in the laboratory. Why is this particular acid preferred to other acids?

Why is the term thermal power plant used ?

What is thermal conductivity of a perfect heat conductor and perfect heat insulator?