Moisture absorbing sheet

Simply lay down a sheet to solve condensation problems

Moisture absorbing sheet


Drykeeper is a non-halogen and environmentally friendly moisture absorbing sheet made by blending synthetic rubber with super absorbent polymer. Drykeeper absorbs a much larger amount of water than silica gel, which is a common desiccant. Unlike pellets and powders, Drykeeper is a thin sheet wrapped in non-woven fabric. It does not take up much space and is extremely easy to handle.


Hygroscopicity is determined by affinity with water, osmotic pressure, and cross-link density. When the water-absorbing polymer in Drykeeper contacts water, water is drawn into the polymer by the action of the ionic groups (that are hydrophilic and easily ionized).
The drawing force is the osmotic pressure*.
The water-absorbing polymer has a three-dimensional network structure and is stabilized in a gel state by the action of rubber elasticity. When the amount of moisture in the surrounding environment decreases, the osmotic pressure expels the drawn-in water to the outside.

  • (Note) Osmotic pressure is the force that causes water to move from the low-density liquid to the high-density liquid between two liquids separated by a cell membrane.

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  • Superior absorption performance
    Absorbs moisture without any saturation, even in high humidity.

Comparison of absorption performance

Comparison of absorption performance
  • (Note) Moisture absorptivity = Percentage change in weight
  • (Note) These values are based on actual measurements and are not guaranteed values.

Comparison of isothermal absorption performance

Comparison of isothermal absorption performance
  • Can be used over a long period of time
    Drykeeper continues to dehumidify over a long period of time thanks to its humidity absorption/release function.

Water absorption capacity

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Water absorption capacity
  • (Note) Products from 2 to 5 years old were tested at FEPS. Products from 7 to 8 years old were collected from customers.
  • Excellent performance even at sub-zero temperatures
    Drykeeper does not harden, even if absorbed moisture freezes in a sub-zero temperature environment.
  • Environmentally friendly
    An environmentally friendly product that does not contain environmentally hazardous substances.

Humidity variations when set in a small distribution panel

Humidity variations when set in a small distribution panel
  • Note: Images are for illustration purposes.
Humidity variations when set in a small distribution panel


  • Drykeeper
  • Drykeeper mini
  • Drykeeper FR
    (flame retardant types)



  • Distribution/control panels
  • Emergency telephones along railway lines
  • Railroad crossing gates
  • Instrument boxes
  • Surveillance cameras
  • Speed limit display panels
  • Mega solar PCS equipment/connection boxes

Recommended installation

We recommend three sheets of Drykeeper (A4 size) for a space of 1m3.


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Absorption 0.8 g(H2O) / 1 g(product)
Daytime 1.3
Working temperature -30°C - 90°C
Recommended replacement period The replacement period differs depending on the usage environment.

Dimensions and packaged quantity

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Product size Thickness (mm) Width (mm) Length (mm) Mass (g) Packaged quantity
A4 size (210 x 300 mm) 2 210 300 160 10 sheets/box
A5L size (105 x 300 mm) 2 105 300 80 20 sheets/box
A5 size (148 x 210 mm) 2 150 210 80 20 sheets/box
Business card size (50 x 100 mm) 2 50 100 13 100 sheets/box
  • (Note) Available in four sizes

Installation method

Use the included hook with an adhesive backing to attach Drykeeper (A4/A5L/A5) to housing parts such as panels.
Attach the included dew condensation indicator to the required position inside the housing.

Installation method
  • (Note) Please do not tear the non-woven fabric bag.
  • (Note) Product specifications are subject to change without notice when necessary to improve products.

Drykeeper mini

Usable in places with limited installation space

Drykeeper mini has an adhesive surface on the back of the sheet, so it is easy to attach.
Drykeeper is made of rubber, so it can be attached to curved surfaces.
The sheet can adhere to resin materials such as ABS, PC, and FRP, and to metals such as SUS, aluminum, and steel.
FEPS will make more detailed proposals according to the assumed usage environment.

Drykeeper mini
Product appearance
Drykeeper mini
Installation example


  • Security cameras
  • LCD monitors
  • Lamps for outdoor use, etc.

Recommended installation

For one liter (1,000 cm³) of space, we recommend two sheets of Drykeeper mini as a guideline.

Recommended installation

Dimensions and packaged quantity

Product size Shipping unit
15 mm x 15 mm x 2 mm 1,260 sheets/box (10 large sheets consisting of 126 Drykeeper sheets each)

Drykeeper FR

Drykeeper enhanced with flame retardant

While maintaining the performance of conventional Drykeeper, it achieves high flame retardancy of grade V-0 under UL 94 standards.

Dimensions and packaged quantity

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Product size Thickness (mm) Width (mm) Length (mm) Mass (g) Packaged quantity
A4 size (210 x 300 mm) 2.3 210 300 200 20 sheets/box
A5 size (148 x 210 mm) 2.3 150 210 100 40 sheets/box


  • Is Drykeeper in compliance with environmental regulations? Drykeeper is compliant with the REACH Regulation and RoHS Directive. Since it is not an electronic device, Drykeeper is not subject to the WEEE Directive.
    If you need any certificates of non-use, please issue a request to our technical staff or use the inquiry form.
  • Are there any precautions when disposing of Drykeeper? Unlike environmentally hazardous inorganic substances such as silica gel (treated as industrial waste), Drykeeper can be treated in the same way as general waste.
  • What if I want to use Drykeeper in a size other than the standard sizes? Depending on the quantity, FEPS may be able to provide a custom size. Please contact FEPS (minimum approx. 35 m² for an order).
    Furthermore, cutting and punching does not affect the moisture absorption and desorption performance of Drykeeper. Therefore, customers may cut/punch the purchased Drykeeper to suit their needs. However, FEPS provides no guarantees in the event of any issues/failures arising from cutting or punching performed by customers.
    • (Note) The blue non-woven fabric that contains Drykeeper has a water repellent effect. This prevents the body of Drykeeper from expanding due to direct contact with water in the unlikely event that condensation occurs. Please use caution when handling Drykeeper without the non-woven fabric after cutting.
  • What is the supported temperature range? The supported temperature range is about -30 to 90°C. Operation will not stop due to freezing even at below freezing point. However, the recommended temperature for the double-sided tape used in the Drykeeper mini is -15 to 80°C. If you plan to use it outside that temperature range, we recommend that you conduct a test to confirm performance.
  • What are some usage examples of Drykeeper? Drykeeper is used in infrastructure equipment, building equipment, electronic equipment, etc., of power companies, expressway companies, and railway companies.
    Roads: ETC devices, display boards, parking lot payment machines
    Railways: Railroad crossing gate, display board
    Airports: Runway guidance lights
    Electronics: Surveillance cameras, servo motors
  • Does Drykeeper have a track record of outdoor use? All Drykeeper products have a track record of outdoor use.
  • Has Drykeeper acquired flame retardant certifications? Regular Drykeeper products have not acquired flame retardant certifications. The flame-retardant type, Drykeeper FR, has acquired grade V-0 grade under the UL 94 standards.
  • Is it possible that mold will grow if Drykeeper remains damp after absorbing moisture? FEPS tested Drykeeper in an environment of normal temperature and high humidity for over one month. We did not observe any mold during the test.

Product inquiries

Furukawa Electric Power Systems Co., Ltd. (Japan)

2-11-16, Azamino-Minami, Aoba-ku, Yokohama-shi, Kanagawa 225-0012 Japan
TEL. +81-45-910-2814 FAX. +81-45-910-2839

Furukawa Electric Trading (SZ) Ltd.

Room 2501, Block A, United Plaza, No.5022 Bin He Road, Futian District, Shenzhen, 518033 PR China
TEL. +86-755-8373-4878-0 FAX. +86-755-8373-4829

Furukawa Electric Europe Limited

Furukawa House,2 Farriers Yard,London, England, W6 8AH
TEL. +44-20-7313-5300 FAX. +44-20-7313-5310

American Furukawa, Inc.

47677 Galleon Drive Plymouth, Michigan USA 48170
TEL. +1-734-446-2200 FAX. +1-734-446-2260