Why does smoke rise in a chimney?

Because the air in passing over the fire becomes heated and therefore lighter, consequently rising, and carrying the smoke with it up through the chimney.

Why is a short chimney liable to have poor draft?

Because the smoke simply rolls out of the chimney before it has attained full velocity, and as the rarified air passes very slowly up the chimney, fresh air flows equally as slowly toward the fire to supply it with oxygen.

Why is a very large chimney liable to have poor draft?

Because the flue is so large that much of the air which goes up the chimney does not become heated, and mixing with the cold air, ascends very slowly.

What are soil and waste vents?

A soil vent is that part of a soil stack which is above the waste entrance of the highest fixture on it, and a waste vent is the same part of a waste stack.

How should batteries of lavatories and sinks be trapped?

Long lines or batteries of fixtures such as lavatories and sinks should have each fixture individually trapped.

Why is it unsanitary to use one trap only to serve a long line of fixtures?

For the reason that there must necessarily be a long line of fouled waste pipe which will throw out foul odors into the room through the waste outlet of each fixture.

What is meant by the conduction of heat?

The transmission of heat from one body to another, when the two bodies are in contact.

What materials convey heat most readily?

Metals, such as gold, silver, platinum, iron, zinc, and tin.

What materials are particularly poor conductors of heat?

Light and porous bodies, such as fur, wool, charcoal, wood, etc.

Are liquids good conductors of heat?

They are not, for the reason that when they are heated, evaporation takes place, and the water passes off in the form of vapor.

How does the presence of oil prevent freezing?

When oil rests on the surface of a liquid, it prevents heat from leaving the liquid, as it is a poor conductor. In this way it prevents the freezing of the liquid.

Can water in an open vessel be heated above 212 degrees?

It can not, for the reason that at this temperature it is converted into steam, and passes off as a vapor.

Is steam visible?

It is not, but in coming in contact with the air it condenses into small drops which are visible.

What are the effects of carbonic acid gas?

It acts like a narcotic poison, and if in sufficient quantity is fatal.

What is the chief source of carbonic acid gas?

It is generated in the decomposition of vegetable and animal matter, and is thrown off in the breath of human beings and animals.

What is the best method of testing stacks in very high buildings?

Such stacks should be tested in sections of not more than 75 ft. in length. If the water test is applied to an entire stack of great length, the pressure of such a high column of water would be enormous, and far greater than the piping should be expected to stand.