The comprehensive guide
Dehumidifiers –
Technology, applications & selection
Which dehumidifier is the right one – and for which industry? This guide explains the basics of humidity, the different types of equipment, and all areas of application from water damage restoration to industrial use. Sound practical knowledge from the DÖLCO drying experts – for over 60 years.
Basics
Understanding air humidity
Air can only absorb water as invisible water vapor – and only up to a temperature-dependent upper limit. The warmer the air, the more moisture it can hold. This results in two central key figures: absolute humidity (g of water per m³ of air) and relative humidity (in %, the ratio to the maximum possible amount).
The temperature dependency is crucial: if warm, moist air cools down on a cold surface, the relative humidity rises there – until the dew point is reached at 100% and water condenses. This is exactly what happens on cold exterior walls, window panes, and pipes. A dehumidifier lowers the water content of the room air and keeps the dew point below the surface temperature – this prevents condensation and thus mold.
For professional damage restoration and building drying, only high-performance devices according to the DÖLCO standard are used – significantly more powerful and robust than standard household appliances.
Technical terms explained
Relative humidity (RH)
Ratio of the existing to the maximum possible amount of water vapor at a certain temperature, in percent.
Absolute humidity
The actual amount of water contained in the air in grams per cubic meter (g/m³).
Dew point
Temperature at which the air can no longer hold its water vapor and condensation occurs – critical on cold components.
Condensation
Transition from water vapor to liquid water as soon as a surface is colder than the dew point (condensation water).
Dehumidification capacity
Amount of water extracted per day (l/24 h) – the most important performance feature of a dehumidifier.
Humidistat
Humidity switch that automatically switches the device off and on again when the setpoint is reached.
Risks
What excessive humidity causes
Too much moisture damages not only the building but also health. Damage often occurs insidiously and only becomes visible after weeks or months – by then, the effort required is already significant.
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Mold
From about 60% relative humidity in the room, the risk of mold increases significantly; from 80% on the surface, most mold species germinate reliably. Spores irritate the respiratory tract, trigger allergies, and can cause chronic ailments.
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Corrosion & rust
Moisture massively accelerates corrosion on metal: at around 90% RH, steel rusts up to six times faster than at 50%. Condensation water loosens protective coatings and attacks fittings, machines, and electronics.
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Material damage
Wood swells and cracks, plaster and masonry are damaged, paper, books, and archives yellow, warp, and stick together. Changes in humidity lead to permanent damage to sensitive materials.
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Health
High humidity is the ideal breeding ground for house dust mites and mold – both common triggers for allergies and respiratory diseases. Asthmatics are particularly sensitive.
Important: the surface counts, not just the room
Mold grows first in the coldest spot. At 22 °C and 50% room humidity, the relative humidity at a wall spot that is only 14 °C cold – for example behind a cupboard on an exterior wall – already reaches around 80%. Mold forms there, even though the room seems "dry". A hygrometer and, in case of doubt, a drying expert provide clarity.
Reference values
Ideal humidity levels by area
There is no universal value – the optimal humidity depends on the intended use. These reference values have proven themselves in practice and according to relevant standards:
| Area | Recommended RH | Note |
|---|---|---|
| Living space | 40 – 50 % | at 20 – 22 °C; mold risk starts above 60% |
| Bedroom & children's room | 40 – 55 % | ventilate regularly, remove moisture at night |
| Basement & storage | 50 – 60 % | watch out for condensation on cold walls in summer |
| Archive & library | 50 % ± 5 % | DIN ISO 11799; fluctuation below 5% RH per 24 h |
| Swimming pool hall | 50 – 65 % | protection of structure and components from condensate |
| Server room & data center | 40 – 60 % | ASHRAE; below 40% static charge, above 60% corrosion |
| Food & pharma | below 60 % | hygiene; prevents bacterial and mold growth |
| Waterworks & technical room | 55 – 65 % | keep dew point always below the coldest pipe surface |
Device types
Equipment types &
functionality
Not every device is suitable for every application. These types are common on the market – the first two are crucial for professional use.
01
Condensation dryer
The most common principle – works like a refrigerator: moist air is cooled via a cold evaporator below the dew point, the water condenses and is collected or pumped out. Most efficient between 15 and 30 °C; performance drops significantly below approx. 10 °C.
02
Adsorption dryer
Binds moisture via a hygroscopic sorbent (silica gel) on a rotor. Works independently of temperature – even in frost down to about -20 °C and at very low humidity. Requires exhaust air ducting for the regeneration air.
03
Peltier dehumidifier
Cools a surface electrically via a Peltier element. Quiet and compact, but low performance – only suitable for very small rooms like cupboards or storage rooms.
04
Granulate dehumidifier
Works without electricity and passively via hygroscopic salts. Very low performance – useful for small, closed areas, not for real drying tasks.
05
Building dryer (mobile, professional)
Robust, transportable condensation dryers for construction sites and water damage – dust and splash-proof, stackable, with large container or condensate pump. The workhorse of the drying industry.
06
Stationary large-scale system
Permanently installed console and industrial units for continuous dehumidification in waterworks, halls, and warehouses – from about 40 to over 2,000 liters of dehumidification capacity per day.
Condensation or adsorption?
The two professional technologies differ primarily in the temperature range. The rule of thumb is simple:
Condensation dryer
Energy-efficient and economical – ideal in heated rooms above 15 °C. No exhaust hose required.
Living & basement rooms · Water damage · Building drying · Swimming pools
Adsorption dryer
Works even in cold, frost, and very low humidity and achieves deep residual moisture levels – but requires higher energy consumption and exhaust air ducting.
Frost & winter construction · Pharma & cleanroom · Process technology · very low target humidity
Rule of thumb: Rooms above 15 °C → condensation dryer. Low room temperatures → DÖLCO K-units with hot gas defrosting. Frost or very low target humidity → adsorption dryer.
Household
Which device for which room?
In the living area, room temperature and moisture accumulation determine the appropriate device type:
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Bathroom
High humidity and warm temperatures – ideal for a condensation dryer.
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Bedroom
A quiet device that works well even at lower temperatures is required – an adsorption dryer or a quiet condensation dryer.
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Living rooms
Condensation or adsorption dryer – both are suitable for living and work rooms at normal room temperature.
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Basement
In cool, unheated basements, a simple condensation dryer loses performance – DÖLCO units with hot gas defrosting or an adsorption dryer are suitable here.
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Storage room
Small closed area – a compact Peltier or granulate dehumidifier is sufficient.
Industries & areas of application
Who needs dehumidifiers –
all areas at a glance
Air dehumidification is much more than water damage and building drying. Wherever moisture endangers building structures, systems, products, or health, DÖLCO devices are used. An overview of the most important industries.
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Water damage restoration
After a pipe burst, flood, or firefighting operation, water penetrates screed, walls, and insulation layers. Rapid drying prevents mold and structural damage.
Recommendation: Mobile condensation dryers; at low temperatures DÖLCO K-units or adsorption dryers · target < 50% RH.
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Building drying & new construction
Screed, plaster, and concrete introduce large amounts of construction moisture. Without dehumidification, construction is delayed; in winter, there is a risk of frost damage.
Recommendation: Mobile condensation dryers & building dryers; in winter construction DÖLCO K-units with hot gas defrosting.
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Screed, insulation layer & cavity drying
Trapped water under the screed and in insulation layers hardly dries out on its own and is a mold nest.
Recommendation: Pressure/suction method plus condensation or adsorption dryer.
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Basements, living rooms & semi-basements
Cold components, lack of ventilation, and laundry drying lead to condensation and mold – especially in summer.
Recommendation: Condensation dryer; in cool basements DÖLCO K-units or adsorption dryers · 50 – 60% RH.
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Archives, museums & libraries
Paper, leather, textile, metal, and data carriers are sensitive. Too humid means mold and corrosion, fluctuations mean material damage.
Recommendation: Stationary, precisely controlled systems · 50% ± 5% RH.
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Warehouse & logistics
Condensation and corrosion protection for goods, machines, and metal parts – avoidance of condensation and mold on stored goods.
Recommendation: Stationary systems or adsorption · usually 45 – 55% RH.
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Food industry & cold storage
Moisture promotes bacteria and spoilage; in cold and freezer storage, condensate freezes into ice – a machine and safety risk.
Recommendation: DÖLCO K-units with hot gas defrosting; in the freezer area adsorption dryers · below 60% RH.
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Pharma & cleanroom
Constant, low humidity is a prerequisite for low-germ production. Above 60%, microorganisms grow, hygroscopic active ingredients clump together.
Recommendation: DÖLCO K-units (condensation dryers) for constant, controlled air humidity.
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Electronics & semiconductor manufacturing
Moisture causes condensation, corrosion, and short circuits; air that is too dry leads to harmful static electricity (ESD).
Recommendation: DÖLCO K-units (condensation dryers) for stable values · usually 40 – 60% RH.
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Swimming pools & wellness
Constant evaporation from the water surface leads to very high hall humidity – without dehumidification, water condenses on the ceiling and structure.
Recommendation: Stationary swimming pool dehumidification, often with heat recovery.
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Waterworks, drinking water & wastewater
Cold water cools pipes and fittings below the dew point – condensation, rust, peeling paint, and damaged electronics are the result.
Recommendation: Stationary, humidity-controlled systems · 55 – 65% RH.
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Industry & production
Defined air humidity ensures consistent product quality, prevents corrosion on systems, and condensation on cold tools.
Recommendation: Stationary systems, condensation or adsorption depending on the process.
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Agriculture & food storage
Grain, seeds, and bulk goods spoil or mold if humidity is too high; seeds lose their germination capacity.
Recommendation: Adsorption dryers, even in cool storage · significantly below mold threshold.
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Server rooms & data centers
Excessive humidity means condensation and corrosion, too low means static electricity with ESD damage to hardware.
Recommendation: Integrated into precision air conditioning · 40 – 60% RH.
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Monument protection, underground garages & ice rinks
Cold, thick walls, unventilated concrete rooms, and cold ice surfaces lead to condensation, salt efflorescence, rust, and mold on building structures and technology.
Recommendation: Adsorption dryers, stationary or temporary · material-friendly constant.
DÖLCO devices
The right devices from DÖLCO
DÖLCO has been developing and manufacturing dehumidifiers in Freiburg for over 60 years – from mobile building dryers to stationary large-scale industrial systems. Here are the most important series with their main areas of application.
Mobile dehumidifiers & building dryers
Robust condensation dryers for water damage, building drying, and storage – stackable, with auto-restart, MID energy meter, and optional condensate pump.
DÖLCO LE-200P22 l/24 h›DÖLCO LE-360033 l/24 h›DÖLCO LE-3600 S33 l/24 h›DÖLCO LE-25000 mini79 l/24 h›DÖLCO LE 2500096 l/24 h›
View all mobile dehumidifiers →Stationary dehumidification systems
Permanently installed console and industrial systems of the K- and T-series for waterworks, energy supply, food industry, and large halls.
DÖLCO K 300044 l/24 h›DÖLCO K 800096 l/24 h›DÖLCO K 25000240 l/24 h›DÖLCO T 750750 l/24 h›DÖLCO T 20002.000 l/24 h›
View all stationary systems →Buying guide
How to choose the
right device
Six criteria for device selection – and the equipment features that matter in professional operation.
01
Room size
Larger rooms require higher dehumidification capacity. Professional devices specify the room size in m³ – DÖLCO systems range from about 60 m³ to 16,000 m³.
02
Temperature
Below 15 °C, condensation dryers lose performance significantly. For frost and winter construction sites, adsorption dryers are the right choice.
03
Initial humidity
With very high component moisture, high-performance devices are necessary. A CM or moisture meter indicates the exact value.
04
Operating time
Continuous operation requires an automatic condensate drain or a condensate pump. For short applications, a large collection container is sufficient.
05
Noise level
For inhabited buildings, choose devices with a low sound pressure level; in the basement or hall, volume does not matter.
06
Energy efficiency
A favorable ratio of dehumidification capacity to power consumption (l/kWh) noticeably reduces operating costs – important in continuous operation.
Equipment that matters
Humidistat
Measures air humidity continuously and switches the device off and on again automatically – keeps the setpoint constant and saves electricity.
Auto-restart
DÖLCO devices restart automatically after a power failure – indispensable for unattended continuous weekend operation.
Condensate pump
Pumps condensate continuously even into higher drains – no annoying container emptying, ideal for long drying processes.
Continuous drain & overflow protection
A fixed drain connection allows continuous operation; the overflow protection prevents the container from overflowing.
MID energy meter
Calibrated consumption and operating hour meter – basis for transparent billing of drying services.
FAQ
Frequently asked questions
Which dehumidifier for which room size?
As a rough guide: For small living rooms, a device with about 8 – 12 l/24 h is sufficient, for medium apartments 16 – 33 l/24 h, for large rooms, construction sites, and commercial use from 30 l/24 h upwards. Professional devices are designed based on room size in m³ – in case of doubt, we will advise you on the correct dimensioning.
Condensation or adsorption dryer?
In rooms above 15 °C, the condensation dryer is the more efficient and economical choice. At low room temperatures, DÖLCO K-units with hot gas defrosting are well suited. Only in frost, sub-zero temperatures, or very low target humidity (pharma, process technology) is an adsorption dryer the only way to go.
What is the ideal air humidity?
In the living area, 40 – 50% relative humidity is considered optimal. From about 60%, the risk of mold increases; below about 30%, mucous membranes dry out. For archives, warehouses, or industry, specific reference values apply depending on the material – see the table above.
Does a dehumidifier help against mold?
Yes – by lowering the humidity below the critical threshold, it deprives mold of its livelihood. Important: A device does not eliminate the cause. In case of visible damage or water damage, the source should be located first – this is the core competence of DÖLCO.
How much electricity does a dehumidifier consume?
This depends on the device class and runtime. Mobile professional condensation dryers typically consume 0.4 – 0.7 kW, large-scale systems significantly more. The efficiency (l water per kWh) is decisive – modern DÖLCO devices work very efficiently here.
Rent or buy a dehumidifier?
For one-time water damage, renting is often worthwhile; for regular use (drying companies, construction, industry), buying is better. DÖLCO offers both as well as advice on the right solution.
Professional consultation
Questions about the right device?
Our expert consultants will help you with device selection and optimal dimensioning for your application – free of charge and without obligation.