Most are free services or you can pay for a more extensive offering where people will actually do some air-sealing or insulating on the spot.
大多是免费服务，也可以支付一个更广泛的提供，人们实际上会做一些空气密封或当场绝缘。
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The greatest single advance began in 1800 when a Frenchman, Nicolas Appert, discovered that he could preserve certain foods by sealing them in jars and keeping the air from them.
The rate of exchange between indoor and outdoor air, which depends on the construction of the house, the ventilation habits of the inhabitants, and the sealing of Windows.