Appliance Thermometers

USDA Meat & Poultry Hotline

1-888-MPHotline

(1-888-674-6854)

The Food Safety and Inspection Service (FSIS) is the public health

agency in the U.S. Department of Agriculture responsible for ensuring

that the nation’s commercial supply of meat, poultry, and egg products

is safe, wholesome, and correctly labeled and packaged.

Food Safety Information

United States Department of Agriculture

Food Safety and Inspection Service

USDA Photo

USDA Photo

Appliance thermometers are specially designed to

measure the temperature of the air in either the

refrigerator/freezer or the oven. Some refrigerator

thermometers have long metal probes and are

similar in appearance to food thermometers. Other

refrigerator thermometers, and most oven

thermometers, are designed to hang from a wire

rack or sit on a shelf.

Whether they measure the temperature in the oven

or refrigerator/freezer, most appliance thermometers

are either liquid-filled or bimetallic-coil thermometers:

• Liquid-filled Thermometers, also called

“spirit-filled” or “liquid in glass”

thermometers, are the oldest types of

thermometers used in home kitchens. As the

temperature increases, the colored liquid

(usually an alcohol solution) inside the

thermometer expands and rises to indicate

the temperature on a scale.

• Bimetallic-coil Thermometers contain a coil

made of two different metals with different

rates of expansion that are bonded together.

The bimetal element is

coiled, fixed at one end,

and attached to a

pointer stem at the

other end. As the

temperature increases,

the pointer will be

rotated by the coiled

bimetal element to

indicate the

temperature.

One of the critical factors in controlling bacteria in food is controlling temperature. Pathogenic microorganisms

grow very slowly at temperatures below 40 °F, multiply rapidly between 40 and 140 °F, and are destroyed at

temperatures above 140 °F. For safety, foods must be held at proper cold temperatures in refrigerators or

freezers and they must be cooked thoroughly. But how would a consumer know if the refrigerator was cold

enough, or if the oven was heating at the proper temperature?

Using Appliance Thermometers

Refrigerator/Freezer Thermometers

Refrigerator/freezer thermometers are specially

designed to provide accuracy at cold temperatures.

For safety, it is important to verify the temperature of

refrigerators and freezers. Refrigerators should

maintain a temperature no higher than 40 °F. Frozen

food will hold its top quality for the longest possible

time when the freezer maintains 0 °F.

Most refrigerators and freezers can be easily

adjusted to run colder or warmer. The temperature

control is usually accessible in the refrigerator part of

the appliance. Check the owner’s manual for specific

details on adjusting the temperature. An adjustment

period is often required when changing the

temperature.

To measure the temperature in the refrigerator:

Put the thermometer in a glass of water and place in

the middle of the refrigerator. Wait 5 to 8 hours. If

the temperature is not 38 to 40 °F, adjust the

refrigerator temperature control. Check again after 5

to 8 hours.

To measure the temperature in the freezer:

Place the thermometer between frozen food

packages. Wait 5 to 8 hours. If the temperature is

not 0 to 2 °F, adjust the freezer temperature control.

Check again after 5 to 8 hours.

An appliance thermometer can be kept in the

refrigerator and freezer to monitor the temperature
Food Safety Questions?

Appliance Thermometers

The USDA is an equal opportunity

 provider and employer.

January 1999

Reviewed Sept 2008 -- No Changes

FSIS encourages the reprint and distribution of this publication for food safety

education purposes. However, USDA symbols or logos may not be used

separately to imply endorsement of a commercial product or service.

Ask Karen!

FSIS’ automated response

system can provide food safety

information 24/7

AskKaren.gov

Call the USDA Meat & Poultry Hotline

If you have a question

about meat, poultry, or

egg products, call the

USDA Meat and

Poultry Hotline

toll free at

1-888-MPHotline

(1-888-674-6854);

TTY: 1-800-256-7072.

 The Hotline is open year-round

Monday through Friday

from 10 a.m. to 4 p.m.

ET (English or

Spanish). Recorded

food safety messages

are available 24 hours

a day. Check out the

FSIS Web site at

www.fsis.usda.gov.

Send E-mail questions to MPHotline.fsis@usda.gov.

at all times. This can be critical in the event of a

power outage. When the power goes back on, if the

refrigerator is still 40 °F and the freezer is 0 °F or

below, the food is safe.

Oven Thermometers

An oven thermometer can be left in

the oven to verify that the oven is

heating to the desired temperatures.

When cooking meat and poultry, it is

important that the oven be set at

325 °F or higher. These

thermometers can measure

temperatures from 100 to 600 °F.

To check the accuracy of an oven, hang the oven

thermometer from a rack in the center of the oven

(you may have to adjust the oven racks). Set the

oven for 325 to 350 °F and allow it to preheat. Once

the oven has reached the set temperature, open

the oven door and read the thermometer. The oven

maintains its temperature by cycling on and off,

especially if the door has been opened. Check the

temperature again after 5 minutes.

If the oven is not maintaining the set temperature,

the oven thermostat will have to be adjusted by a

service center representative authorized by the

manufacturer. However, if, after testing the oven

temperature at several settings (325, 350, 375, and

400 °F), it is consistently high or low by the same

amount (say, 25 °F), this can be factored into the

temperature setting. For example, if you know that

your oven runs “hot” by 25 °F and you need to bake

something at 350 °F, set the oven for 325 °F. Always

check the oven thermometer to verify the

temperature.

Microwave Oven Probes

A microwave oven probe can be plugged into the

microwave and inserted in the food being cooked.

Some microwaves can be programmed to cook the

food until a desired temperature is reached. Check

the owner’s manual for more information. Some

thermometers are specially designed to be used in

the microwave oven, but most food thermometers are

not microwave-safe. Check the packaging instructions

for more information.