B-D Fever Thermometers – A Century of Accuracy and Trust

Few household objects were as quietly important to 20th-century life as the humble fever thermometer — and few names in this field were more respected than Becton, Dickinson & Co., better known simply as B-D. For over a century, B-D’s glass oral and rectal thermometers were a fixture in homes, hospitals, and doctors’ bags across America.

From their precise mercury columns to their distinctive red- or blue-tinted tips, these instruments became a symbol of reliability in times of illness. Today, they stand as collectible relics of a medical era defined by craftsmanship and trust.

Origins: Becton, Dickinson & Co. Enters the Thermometer Market

Founded in 1897 in Rutherford, New Jersey, Becton, Dickinson & Co. quickly established itself as a manufacturer of precision medical instruments — syringes, needles, and glassware. By the early 1900s, the company expanded into clinical thermometers, competing with European makers who had long dominated the market.

These early B-D thermometers were hand-calibrated, with etched numerals filled with enamel paint for clarity. They were crafted from solid, laboratory-grade glass and built to last decades if handled with care.

Oral vs. Rectal: A Standard is Born

In the first decades of the 20th century, there was no universal way to differentiate oral and rectal thermometers. B-D helped pioneer a now-standard safety convention:

• Oral thermometers were made longer, with clear or blue-tinted tips.

• Rectal thermometers were shorter, sturdier, and tipped in red glass to avoid dangerous mix-ups.

This color coding became so widely adopted that it’s still recognized globally.

The Mercury Column and Constriction

The defining feature of these thermometers was their mercury column. Mercury expands predictably with heat, and inside a sealed glass tube, it could precisely indicate body temperature.

B-D fever thermometers incorporated a tiny constriction just above the bulb. When the mercury expanded during a reading, it passed this choke point — but when the thermometer cooled, the mercury above the constriction stayed in place. This allowed the reading to be taken after removal from the patient, a huge convenience in an era before digital displays.

To reset the thermometer, one simply “shook it down” with a quick snapping motion of the wrist — a ritual anyone who grew up before the 1990s will remember vividly.

World War II and the Push for Domestic Production

During World War II, medical supply shortages made U.S. manufacturing more critical than ever. B-D became a major supplier of clinical thermometers to the U.S. military and civilian hospitals alike.

Cases from this era were often nickel-plated brass or aluminum tubes with screw-on caps, sometimes lined with felt or paper to protect the glass. Postwar, these rugged designs gave way to more modern, consumer-friendly packaging.