Until about 250 years ago, households did not take dirt as (1)....... as they do now - it was a fact of life, and that was that. Cleaning often consisted of an annual (2)....... called 'spring cleaning' when the furniture was moved aside, and all the linen products in the house were cleaned. Carpets and rugs were taken outside, hung on ropes and had the dust (3)....... out of them - an exhausting and messy process.

The industrial revolution brought about a major change - as new (4)....... became available to make homes cleaner, a corresponding interest in '(5).. hygiene' appeared in households. This in turn led to the (6)....... of further products, one of which was the vacuum cleaner.

(7)....... has it that when one of the first vacuum cleaners was demonstrated, a kindly scientist took the proud inventor (8)....... , and offered a bit of advice that was to become (9).. to the future evolution of the product - 'make it suck, not blow'.

The first vacuum cleaners appeared in the 1860s in the United States. They were operated by hand pumps and were almost as (10)....... as spring cleaning. It was only when electric motors had become sufficiently (11)....... to become portable that vacuum cleaners became common household items. Most of today's major (12)....... - including Electrolux and Hoover - were born in the 1920s.

The household (13)....... that vacuum cleaners suck up is mostly dead skin cells - humans (14)....... millions of cells every day. A much smaller proportion comes from dust and soil carried into the house from (15)....... .