Server room monitoring: which temperature and humidity apply?
In many organisations the server sits in a side room, in the basement or in a cabinet in the office. If the air conditioning fails there, often nobody notices until IT stops working. This guide shows which temperature and humidity ranges are recommended, where to measure and what the German IT-Grundschutz modules say about it.
- Temperature: for equipment classes A1 to A4, ASHRAE recommends 18 to 27 °C for the air entering the equipment. This is a recommendation, not a regulation.
- Humidity: the recommended range is a dew point between −9 and 15 °C with no more than 70 % relative humidity, without condensation.
- Where to measure: the values refer to the equipment's air inlet, not to the air somewhere in the room.
- What counts for your equipment: the limits in the manufacturer's data sheet.
- BSI: for server rooms, module INF.2 requires temperature and humidity to be recorded so that exceedances can be identified afterwards.
- Frigo during a power cut: the connectivity unit keeps running for about four hours on its built-in battery.
Who this guide is for
- SMEs, medical practices and law firms with their own server room or server cabinet
- Offices with a network cabinet, switches or a small server in a side room
- Building services and facility management teams looking after technical rooms
Data centres are subject to further requirements, such as the full BSI module INF.2. This guide is aimed at smaller rooms and cabinets where nobody works permanently.
Which values does ASHRAE recommend?
The central reference, which the US Department of Energy also relies on, comes from technical committee TC 9.9 of the US professional body ASHRAE. Its “Thermal Guidelines for Data Processing Environments” (5th edition, 2021) distinguish two kinds of range:
- Recommended range: the range that data centres should be designed and operated to target for high reliability and energy-efficient operation.
- Allowable ranges by class A1 to A4: the limits within which manufacturers test their equipment for functionality. The US Department of Energy points out that these limits cover functionality, not reliability.
| Range | Temperature at air inlet | Humidity (non-condensing) |
|---|---|---|
| Recommended, A1 to A4 | 18 to 27 °C | dew point −9 to 15 °C, max. 70 % RH (or 50 % RH, see below) |
| Allowable A1 | 15 to 32 °C | up to dew point 17 °C and 80 % RH |
| Allowable A2 | 10 to 35 °C | up to dew point 21 °C and 80 % RH |
| Allowable A3 | 5 to 40 °C | up to dew point 24 °C and 85 % RH |
| Allowable A4 | 5 to 45 °C | up to dew point 24 °C and 90 % RH |
For all four allowable classes the lower humidity limit is a dew point of −12 °C or 8 % RH, whichever means more moisture. The values come from the ASHRAE TC 9.9 reference card for the 2021 edition. For high-density servers ASHRAE has a separate class H1 with a narrower range.
Why humidity is given as a dew point
ASHRAE states humidity as a combination of dew point and relative humidity. The dew point stands for the amount of water in the air, while relative humidity also depends on temperature. The same relative humidity can therefore be inside or outside the range depending on the temperature. A sensor that measures temperature and relative humidity provides both values from which the dew point follows.
Which class applies to your equipment
This is stated in the manufacturer's data sheet. For small technical rooms the BSI also refers to the limits in the data sheets of the equipment operated there. According to ASHRAE, tape drives need a more stable and more restrictive environment than other equipment.
Where to measure: at the air inlet, not anywhere in the room
The ASHRAE ranges apply to the air entering the IT equipment. The US Department of Energy's data centre guide therefore recommends temperature and humidity sensors at the air inlet of the equipment, at the heights specified by ASHRAE. On a rack, this is the side where the equipment draws in air, often the front. Check the airflow direction of your equipment.
IT equipment turns its electrical power into heat, so warmed air leaves at the back. A sensor at the back or under the ceiling therefore does not show the value the recommendation is based on. The guide also provides for monitoring temperature and humidity at the supply air of each air-conditioning unit.
Would you notice if the air conditioning failed on a Saturday?
Get your setup →What happens when it is too warm, too humid or too dry?
| Condition | What the sources say |
|---|---|
| Too warm | If temperature or humidity are outside the manufacturer's limits, components may malfunction or fail (BSI). Even above the recommended range, server fans may run faster and use more power, according to the US Department of Energy. |
| Too humid | All ASHRAE ranges apply only without condensation. If a test with copper and silver coupons shows corrosive pollutants in the air, ASHRAE advises keeping relative humidity at 50 % or below. |
| Too dry | In very dry air the risk of electrostatic charge rises. According to the research cited by ASHRAE, the increase between 25 % and 8 % RH is small. As minimum requirements ASHRAE names conductive or grounded furniture and a grounded wrist strap when working on hardware. |
Electrostatic discharge can damage or destroy sensitive components, the BSI writes, and it recommends a static-dissipative floor covering for technical rooms. ASHRAE points out that rooms without static-dissipative floors, where people work without ESD shoes, may need higher humidity.
What the BSI requires under IT-Grundschutz
In its IT-Grundschutz Compendium (Edition 2023), the German Federal Office for Information Security (BSI) describes two modules that are relevant here. The Compendium is a BSI standard, not a law. Whether it is binding for your organisation depends on whether you apply IT-Grundschutz or are obliged to do so by contract or regulation. Please clarify this case by case. The BSI is a German authority. In Austria and Switzerland, please clarify which requirements apply to your organisation.
INF.2 Data centre and server room
- INF.2.A5 (basic): air temperature and humidity must stay within the specified limits. Air conditioning must be maintained regularly. Temperature and humidity must be recorded so that it can be seen afterwards whether limits were exceeded, and so that the data helps to find the cause.
- INF.2.A11 (basic): infrastructure such as leak detection, air-conditioning, power and UPS systems must be monitored automatically. In a server room, equipment that is rarely operated should have a remote fault indicator, and the people responsible must be alerted promptly.
- INF.2.A16 (standard): all relevant climate values should be monitored continuously, with an automatic alert if a value deviates.
INF.5 Room or cabinet for technical infrastructure
For small environments, such as an organisation with a few workstations and one server in a separate room, the BSI says it is often enough to implement module INF.5 instead of INF.2. Its requirements can also be applied to a cabinet if a separate room is not possible.
- INF.5.A10 (standard): temperature and humidity should stay within the limits in the equipment's data sheets, with an adequately sized ventilation or air-conditioning system.
- INF.5.A11 (standard): water, waste water and heating pipes should not run through the room.
- INF.5.A3 and A7 (basic): the room must be protected against unauthorised access and must not be used for other purposes, such as storage.
And EN 50600?
The EN 50600 series covers data centre facilities and infrastructures. The BSI cites part 1 as describing general principles for the design of data centres and aligns its definition of data centre and server room with it methodologically. We do not reproduce specific climate values from the standard here, as we could not consult the text freely.
Where manual checks leave gaps
- Air conditioning fails at night or at the weekend. Failures often develop gradually and are noticed too late without active monitoring, the BSI writes.
- Power cut. Ventilation can fail together with the power. If it is not ready afterwards, the room heats up, the BSI writes.
- Water and leaks. Leaking pipes, heavy rain or a faulty air-conditioning unit can bring water into the room. A temperature and humidity sensor does not reliably detect water on the floor. Dedicated leak sensors exist for that, and Frigo offers them too.
- Server cabinet in the office. The cabinet depends on the office climate. You cannot see from outside whether the values inside the cabinet are within the data sheet limits.
- Door left open, room used for other purposes. The room serves as storage, the door stays open, unauthorised people have access. The BSI requires access protection and rules out other uses.
- No record. Without a history you cannot show whether and for how long limits were exceeded.
What a sensor adds
A sensor measures temperature and relative humidity at the air inlet around the clock, alerts the people you name by app and email when a value leaves your limit, and writes every deviation with start, end and duration to a continuous, time-stamped record. A monthly PDF report per sensor is created automatically, and you can export at any time. This supports your documentation, for example the recording under INF.2.A5. Whether it is sufficient in your case is set by your security concept. Where it makes sense, a door or opening contact can also be used.
The sensors stick on, without drilling or cables, and take less than five minutes per sensor to install. The connectivity unit needs a power socket and has its own mobile connection, so no Wi-Fi is needed. If a sensor or the connectivity unit stops sending data, Frigo alerts the named people.
Important: Frigo measures the air at the sensor's location. It does not cool anything, does not control any air-conditioning unit and does not prevent failures. It alerts you earlier and keeps a record. Only a dedicated leak sensor detects water on the floor.
If power fails, the connectivity unit keeps running on its built-in battery for about four hours. During that time Frigo keeps measuring and alerts you when a value leaves your limit, as long as the mobile network is available. Once the battery is empty, Frigo reports that the connectivity unit has stopped sending data. The sensors do not store readings, so there is no data for that period. New readings arrive once the connectivity unit has power again. If only the air-conditioning unit fails, Frigo alerts you without this time limit.
How the system is built is explained under How does Frigo work?.
Four things to set per room or cabinet
- the measuring point at the air inlet of the rack or cabinet
- the limits for temperature and humidity, based on the equipment's data sheet
- who is notified, including at night and at the weekend
- who checks on site and what to do then
Frequently asked questions
What temperature is recommended for a server room?
For equipment classes A1 to A4, ASHRAE TC 9.9 recommends 18 to 27 °C for the air entering the equipment. The allowable ranges per class are wider, for example 15 to 32 °C for A1. What counts for your equipment are the limits in the manufacturer's data sheet.
What humidity is right for a server room?
The ASHRAE recommended range is a dew point between −9 and 15 °C with no more than 70 % relative humidity, without condensation. If a test shows corrosive pollutants in the air, ASHRAE advises no more than 50 % relative humidity.
Where should the sensor go in a server room?
At the air inlet of the equipment, which on a rack is where the equipment draws in air, often the front. The ASHRAE values refer to this point, and the US Department of Energy's data centre guide recommends the same. Warmed air leaves at the back.
Do I have to record the temperature in the server room?
If you apply IT-Grundschutz, BSI module INF.2 requires server rooms to record temperature and humidity so that exceedances can be identified afterwards. For small environments module INF.5 is often enough, which recommends staying within the data sheet limits. Please clarify case by case whether this is binding for you.
Does a humidity sensor detect water damage?
Not reliably. It measures humidity in the air, not water on the floor. Dedicated leak sensors exist for leaks, and Frigo offers them too. The BSI explicitly names leak detection as part of automatic infrastructure monitoring.
Does Frigo work during a power cut?
Yes, for a limited time. The connectivity unit has a built-in battery and keeps running for about four hours during a power cut. During that time Frigo keeps measuring and alerts you when a value leaves your limit, as long as the mobile network is available. Once the battery is empty, Frigo reports that the connectivity unit has stopped sending data. The sensors do not store readings, so there is no data for that period. New readings arrive once the connectivity unit has power again. If only the air-conditioning unit fails, Frigo alerts you without this limit.
Sources
- ASHRAE TC 9.9: 2021 Equipment Thermal Guidelines for Data Processing Environments, Reference Card (from Thermal Guidelines, 5th edition, © 2021, 2024, USA)
- U.S. Department of Energy, Federal Energy Management Program (FEMP): Best Practices Guide for Energy-Efficient Data Center Design (revised July 2024, USA)
- German Federal Office for Information Security (BSI): IT-Grundschutz module INF.2 Data centre and server room (Edition 2023, Germany, in German)
- German Federal Office for Information Security (BSI): IT-Grundschutz module INF.5 Room or cabinet for technical infrastructure (Edition 2023, Germany, in German)
- German Federal Office for Information Security (BSI): IT-Grundschutz Compendium, Edition 2023 (available since 1 Feb 2023, accessed October 2026, Germany, in German)
Your server room in view
See a deviation before IT stops working, and have the record automatically.
To IT & facilities →This article is guidance, not legal advice. It reproduces recommendations from professional bodies and authorities, which can differ. What counts are the regulations that apply to you, the requirements of the competent bodies and the information from equipment manufacturers. Frigo measures the air at the sensor's location, does not cool anything, does not control any air-conditioning unit and does not prevent failures. Alerts require a working connection. During a power cut the connectivity unit keeps running on its built-in battery for about four hours, after that Frigo reports that the connectivity unit has stopped sending data. Sources as of: October 2026.