Horiba Mexa-200
Science History Institute/Gregory Tobias
Horiba Mexa-200

Science History Institute/Gregory Tobias

It was quite fortunate for us that our MEXA analyzer was adopted as the standard device by the EPA because it became the world standard as a result. Every car manufacturer in the world needed the MEXA analyzer to be certified by the EPA.

―Masao Horiba

The Horiba Mexa-200 is a prime example of how an instrument can be modified for different purposes and how the demands of current and potential users can lead to important changes in instrument features.

In the early 1960s Masao Horiba’s company was still young, with just two significant products: an electrode pH meter and the infrared gas analyzer used in medicine. The Japanese government was interested in the possibilities of the gas analyzer: could it be adapted to create a car-exhaust analyzer? Masao Horiba knew that chemically the proposed use could work, as he mentioned in his the Institute oral history:

A sort of combustion occurs in the human body, and we exhale a sort of exhaust gas. So the theory works the same for the combustion in a gasoline engine.

But he was not sure it would really work: the infrared gas analyzer had been used in a clean environment for clean tests, and its proposed new use was anything but clean.

Luckily, Horiba scientist Masahiro Oura pursued the idea, and in 1964 the Mexa-1 was released. In 1969 the Horiba Corporation launched the Mexa-200 CO analyzer, which had a sample probe that could be placed in an automobile tailpipe. But Horiba also had to make other considerations: the nonscientist operators and heavy use meant the instrument needed to be simpler and more durable and reliable than previous instruments. With these issues solved, Horiba approached three major U.S. auto manufacturers with its new device, and after they had embraced the instrument, the Mexa-200 was adopted by the U.S. Environmental Protection Agency to regulate all auto emissions. As emissions regulations became more stringent, the Horiba Corporation adapted its products to become even more sensitive to the tiny amounts of particulates cars might be releasing into the atmosphere.

Mexa-200: One of the earliest instruments used to measure exhaust pollutants in the air

Research fellow David Brock discusses the Mexa-200.