Room temperature in the lab: what 15–25 °C means, and ambient vs controlled

Room temperature is usually defined as 15 to 25 °C (59 to 77 °F); in everyday speech it means about 20 °C. In everyday use the phrase isn't precise: a kitchen in winter and an office in a heatwave can differ by fifteen degrees. In a laboratory the phrase has a set meaning, usually 15 to 25 °C, and labels on reagents use more exact wording still. This guide explains where the 15–25 °C range comes from, the difference between ambient and controlled room temperature, what common storage labels mean, and how to check the temperature of a room.

It completes the set with fridge temperatures and freezer temperatures. Terms are defined in the glossary.

What is room temperature?

In everyday speech, room temperature is simply whatever a comfortable indoor room happens to be, usually somewhere around 18 to 22 °C. That is too vague for storing materials, so pharmacopoeias and regulators define it.

The European and WHO figures are summarised by the ECA Academy, and the US figure comes from USP.

So when a lab supplier or a method says "room temperature", it almost always means 15 to 25 °C.

Room temperature in Celsius, Fahrenheit and kelvin (°C, °F, K)

To convert Celsius to kelvin, add 273.15. To convert to Fahrenheit, multiply by 9/5 and add 32. See melting, boiling and freezing points for more on temperature scales. The kelvin values matter when temperature goes into an equation, such as the Arrhenius equation.

Ambient vs controlled room temperature

Ambient means whatever the surroundings are; controlled means held within a set range, such as 20 to 25 °C in the US Pharmacopeia, and monitored (USP). The two terms are often used as if they were the same.

• Ambient temperature is the temperature of the surroundings, whatever it happens to be. A shelf, a warehouse, a parcel in a van and a car boot are all "ambient", and they can range from below freezing to well above 30 °C.
• Controlled room temperature means the temperature is actively held within a range, usually by heating and air conditioning, and checked.

The difference matters most in transit and in unheated stores. A parcel described as "shipped at ambient temperature" isn't kept at 15 to 25 °C. It simply isn't cooled. See why freeze-dried peptides ship at room temperature for why that is fine for a dry powder over a few days.

What storage labels mean

Reagent and medicine labels avoid "room temperature" and state a limit instead (EMA).

A label of "do not store above 25 °C" doesn't mean the material is ruined at 26 °C. It means the maker's stability data supports storage up to that limit. For how much warmth speeds up breakdown, see the Arrhenius equation.

Room temperature and stability

A room is never at one steady temperature. It warms during the day, cools at night and changes with the seasons. Stability studies deal with this by testing at a fixed temperature that stands in for the real range.

European guidance explains that continuous storage at 25 °C in a stability study covers the temperatures likely to be met under ambient conditions across Europe, including short spells above 25 °C (EMA). It does this through mean kinetic temperature: a single figure that gives the same amount of breakdown as a varying temperature. Warm spells count for more than cool ones. See the Arrhenius equation for how it is worked out.

For freeze-dried peptides, a few days at room temperature makes little difference, but months do. See how long freeze-dried peptides last at room temperature.

Keeping materials at room temperature well

• Avoid warm spots. Windowsills, the tops of fridges, shelves above radiators and spots near equipment exhausts can be far warmer than the room.
• Keep out of direct sun. Sunlight warms a container well above the air around it, and light can break down some compounds.
• Keep things sealed and dry. At room temperature, moisture often matters as much as heat. See humidity, dew point and condensation.
• Don't use a car or van as storage. A closed vehicle in summer can get far hotter than any room.

Checking room temperature

Thermometers

A simple digital thermometer shows the temperature now. A min/max thermometer also records the highest and lowest temperatures since it was last reset, which shows what happened overnight or over a weekend.

Data loggers

A temperature data logger records readings at set intervals, so you can see the full pattern of a room over days or weeks. It is the best way to show that a store stays within 15 to 25 °C through the seasons.

Placing the sensor

Put the sensor where the materials are kept, not near a door, window, radiator or air vent. A room can differ by several degrees between floor and ceiling, so measure at the height of the shelves you use.

How we store our stock

We store freeze-dried peptides at −20 °C, sealed and protected from light, rather than at room temperature. Each product page lists the recommended storage condition for that compound. See how to store freeze-dried peptides for storage in more detail. We ship UK orders at ambient temperature; see how we ship.

Related guides

For colder storage, see fridge temperatures, freezer temperatures and, at the bottom of the scale, liquid nitrogen and cryogenic storage. For converting between units, see SI units and prefixes. An independent lab tests every lot we sell for purity by HPLC and identity by mass spectrometry. Every lot has its own COA, published on the product page and on that lot's own page. See Quality.