No single level of relative humidity provides adequate moisture content
in all hygroscopic materials. Moisture content requirements vary greatly from
one material to the next. We will discuss typical hygroscopic materials which
require specific RH levels to avoid moisture loss and materials deterioration
and/or production problems that result.
|
Recommended Relative
Humidities
|
|||
|
Process or Product
|
Temp. °C
|
%RH
|
|
|
Residences
|
21-22
|
30
|
|
|
Libraries & Museums
|
|||
|
Archival
|
13-18
|
35
|
|
|
Art storage
|
16-22
|
50
|
|
|
Stuffed fur animals
|
4-10
|
50
|
|
|
Communication Centers
|
|||
|
Telephone terminals
|
22-26
|
40-50
|
|
|
Radio & TV studios
|
23-26
|
30-40
|
|
|
General Commercial & Public Buildings(including cafeterias,
restaurants airport terminals, office buildings & bowling centers)
|
21-23
|
20-30
|
|
|
Hospitals & Health Facilities
|
|||
|
General clinical areas
|
22
|
30-60
|
|
|
Surgical area
|
|||
|
Operating rooms
|
20-24
|
50-60
|
|
|
Recovery rooms
|
24
|
50-60
|
|
|
Obstetrical
|
|||
|
Full-term nursery
|
24
|
30-60
|
|
|
Special care nursery
|
24-27
|
30-60
|
|
|
Manufacture
|
26
|
50
|
|
|
Ceramics
|
|||
|
Refractory
|
43-66
|
50-90
|
|
|
Molding Room
|
27
|
60-70
|
|
|
Clay Storage
|
16-27
|
35-65
|
|
|
Decalcomania production
|
24-27
|
48
|
|
|
Decorating Room
|
24-27
|
48
|
|
|
Cereal
|
|||
|
Packaging
|
24-27
|
45-50
|
|
|
Distilling
|
|||
|
Storage
|
|||
|
Grain
|
-14
|
35-40
|
|
|
Liquid Yeast
|
0-1
|
||
|
General manufacturing
|
16-24
|
45-60
|
|
|
Aging
|
18-22
|
50-60
|
|
|
Electrical Products
|
|||
|
Electronics & X-ray:
|
|||
|
Coil & transformer winding
|
22
|
15
|
|
|
Semi conductor assembly
|
20
|
40-50
|
|
|
Electrical instruments:
|
|||
|
Manufacture & laboratory
|
21
|
50-55
|
|
|
Thermostat assembly
|
24
|
50-55
|
|
|
& calibration
|
|||
|
Humidistat assembly
|
24
|
50-55
|
|
|
& calibration
|
|||
|
Small mechanisms:
|
|||
|
Close tolerance assembly
|
22
|
40-45
|
|
|
Meter assembly & test
|
24
|
60-63
|
|
|
Switchgear:
|
|||
|
Fuse & cutout assembly
|
23
|
50
|
|
|
Capacitor winding
|
23
|
50
|
|
|
Paper Storage
|
23
|
50
|
|
|
Conductor wrapping with yarn
|
24
|
65-70
|
|
|
Lightning arrester assembly
|
20
|
20-40
|
|
|
Thermal circuit breakers
|
|||
|
assembly & test
|
24
|
30-60
|
|
|
High-voltage transformer repair
|
26
|
55
|
|
|
Water wheel generators:
|
|||
|
Thrust runner lapping
|
21
|
30-50
|
|
|
Rectifiers:
|
|||
|
Processing selenium &
|
23
|
30-40
|
|
|
copper oxide plates
|
|||
|
Fur
|
|||
|
Storage
|
4-10
|
55-65
|
|
|
Gum
|
|||
|
Manufacturing
|
25
|
33
|
|
|
Rolling
|
20
|
63
|
|
|
Stripping
|
22
|
53
|
|
|
Breaking
|
23
|
47
|
|
|
Wrapping
|
23
|
58
|
|
|
Leather
|
|||
|
Drying
|
20-52
|
75
|
|
|
Storage, winter room temp.
|
10-16
|
40-60
|
|
|
Lenses (Optical)
|
|||
|
Fusing
|
24
|
45
|
|
|
Grinding
|
27
|
80
|
|
|
Matches
|
|||
|
Manufacture
|
22-23
|
50
|
|
|
Drying
|
21-24
|
60
|
|
|
Storage
|
16-17
|
50
|
|
|
Mushrooms
|
|||
|
Spawn added
|
16-22
|
**
|
|
|
Growing period
|
10-16
|
80
|
|
|
Storage
|
0-2
|
80-85
|
|
|
Paint Application
|
|||
|
Oils, paints: Paint Spraying
|
16-32
|
80
|
|
|
Plastics
|
|||
|
Manufacturing areas:
|
|||
|
Thermosetting molding
|
|||
|
compounds
|
27
|
25-30
|
|
|
Cellophane wrapping
|
24-27
|
45-65
|
|
|
Plywood
|
|||
|
Hot pressing (resin)
|
32
|
60
|
|
|
Cold pressing
|
32
|
15-25
|
|
|
Rubber-Dipped Goods
|
|||
|
Cementing
|
27
|
25-30*
|
|
|
Dipping surgical articles
|
24-27
|
25-30*
|
|
|
Storage prior to manufacture
|
16-24
|
40-50*
|
|
|
Laboratory (ASTM Standard)
|
23
|
50*
|
|
|
* Dew point of air must be below
evaporation temperature of solvent
** Nearly saturated |
|||
|
Tea
|
|||
|
Packaging
|
18
|
65
|
|
|
Tobacco
|
|||
|
Cigar & cigarette making
|
21-24
|
55-65
|
|
|
Softening
|
32
|
85-88
|
|
|
Stemming & stripping
|
24-29
|
70-75
|
|
|
Packing & shipping
|
23-24
|
65
|
|
|
Filter tobacco casing
|
24
|
75
|
|
|
& conditioning
|
|||
|
Filler tobacco storage
|
25
|
70
|
|
|
& preparation
|
|||
|
Wrapper tobacco storage
|
24
|
75
|
|
|
& conditioning
|
|||
|
Pharmaceuticals
|
|||
|
Powder storage (prior to mfg)
|
*
|
*
|
|
|
Manufactured powder storage
|
|||
|
& packing areas
|
24
|
35
|
|
|
Milling room
|
24
|
35
|
|
|
Tablet compressing
|
24
|
35
|
|
|
Tablet coating room
|
24
|
35
|
|
|
Effervescent tablets
|
|||
|
and powders
|
24
|
20
|
|
|
Hypodermic tablets
|
24
|
30
|
|
|
Colloids
|
24
|
30-50
|
|
|
Cough drops
|
24
|
40
|
|
|
Glandular products
|
24
|
5-10
|
|
|
Ampoule manufacturing
|
24
|
35-50
|
|
|
Gelatin capsules
|
24
|
35
|
|
|
Capsule Storage
|
24
|
35
|
|
|
Microanalysis
|
24
|
50
|
|
|
Biological manufacturing
|
24
|
35
|
|
|
Liver extracts
|
24
|
35
|
|
|
Serums
|
24
|
50
|
|
|
Animal rooms
|
24-27
|
50
|
|
|
Small animal rooms
|
24-26
|
50
|
|
|
* store in sealed plastic
containers in sealed drums.
|
|||
|
Photographic Processing
|
|||
|
Photo studio
|
|||
|
Dressing room
|
22-23
|
40-50
|
|
|
Studio (camera room)
|
22-23
|
40-50
|
|
|
Film darkroom
|
21-22
|
45-55
|
|
|
Print darkroom
|
21-22
|
45-55
|
|
|
Drying room
|
32-38
|
35-45
|
|
|
Finishing room
|
22-24
|
40-55
|
|
|
Storage room
|
|||
|
b/w film & paper
|
22-24
|
40-60
|
|
|
color film & paper
|
4-10
|
40-50
|
|
|
Motion picture studio
|
22
|
40-55
|
|
|
Static Electricity Control
|
|||
|
Textiles, paper, explosive control
|
>55
|
||
|
Clean Rooms & Spaces
|
45
|
||
|
Data Processing
|
22
|
45-50
|
|
|
Paper Processing
|
|||
|
Finishing area
|
21-24
|
40-45
|
|
|
Test laboratory
|
23
|
50
|
|
