A desiccant system in which a body of water-vapor-adsorbing desiccant
material is sealed in a bag which is permeable to water vapor, but
not to liquid water or particulates. A humidity indicator is sealed
to the bag, and is sensitive to humidity within the bag, but not
to water or water vapor outside the bag. The indicator changes color
when a predetermined humidity level has been reached within the
bag, and thereby to signal that the bag should be replaced.
1. A desiccant system, comprising a bag made of a material which
is permeable to water vapor, and impermeable to liquid water and
particulates, a desiccant material sealed in the bag, and a humidity
indicator secured to the bag to sense humidity within the bag, and
to be insensitive to water vapor outside the bag.
2. The system defined in claim 1 in which the humidity indicator
changes color to signal when a predetermined humidity within the
bag has been reached.
3. The system defined in claim 2 in which the humidity indicator
is calcium chloride.
4. The system defined in claim 1 in which the bag is made of a
spun-bonded polyolefin sheet material.
5. The system defined in claim 1 in which the desiccant material
comprises a mixture of calcium chloride, Montmorillonite clay, and
6. The system defined in claim 5 and in which the desiccant material
further comprises scented plastic beads.
CROSS REFERENCE TO RELATED APPLICATION
 This application claims the benefit of U.S. Provisional
Application No. 60/300701 filed Jun. 25 2001.
BACKGROUND OF THE INVENTION
 This invention relates to a desiccant bag for adsorbing
water vapor from a surrounding space, and having an integrated humidity
indicating card which changes color when the adsorption capacity
of the bag reaches a level where the bag should be discarded and
replaced. The bag finds particular utility in adsorbing water vapor
from spaces such as boat cabins and storage areas, stored automobiles,
closets, drawers and other home spaces, and storage areas in a seaside
location which are especially susceptible to high humidity and damage-causing
SUMMARY OF THE INVENTION
 The desiccant system of this invention comprises a desiccant
material sealed in a bag made of a material, preferably spun-bonded
polyolefin sheet material, which is permeable to water vapor, and
impermeable to liquid water and particulates. A humidity indicator
secured to an outer surface of the bag senses the humidity level
within the bag, and signals, preferably by a color change, when
the adsorbing ability of the desiccant material is exhausted and
the moisture-adsorbing desiccant system should be discarded and
replaced. The desiccant material may include pleasantly scented
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 is a front elevation of a desiccant bag according
to the invention; and
 FIG. 2 is a sectional view on line 2-2 of FIG. 1 and additionally
showing a foil container for storing the bag until it is to be used.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to the drawings, a desiccant bag 10 is made of
a porous material which is permeable to, and will pass water vapor,
but is impervious to liquid water, dust, and other particulates.
A preferred plastic sheet material for the bag is a spun-bonded
polyolefin marketed by E. I. duPont under the trademark TYVEK.RTM.
with a thickness in a range of 2.0 to 9.1 mils, and typically of
about 5.3 mils.
 A humidity indicator 11 is in the form of a self-adhesive
rectangular card which is adhered to an outer surface of the bag.
Only the rear surface of the card facing the bag outer surface senses
humidity within the bag, and the card front surface is covered with
a transparent and impervious plastic sheet to be isolated from the
outside environment. Humidity indicators or markers of this type
use a humidity-sensing color-change material 13 such as cobalt chloride,
and are available from Desiccare, Inc., in Santa Fe Springs, Calif.,
assignee of the present invention. This material will change color
from, for example, blue to pink or red when a specific humidity
level (e.g., typically 50% or 60% depending on the application)
is reached within the bag. The bag is then discarded, and replaced
with a fresh desiccant bag.
 The bag is filled with about six to seven ounces (for the
illustrated bag size of about 8 to 9 inches high and about 4 to
41/2 inches wide) of a desiccant material 15 of the following presently
 22% calcium chloride
 30% Montmorillonite clay.
 Balance of diatomacious earth which absorbs water. About
5 grams of polyethylene pellets entrained with pleasantly scented
material such as lemon oil are added to this mixture. Scented plastic
beads of the type described above are available from Aroma Tech
in Somerville, N.J., and Polyvel in Hammonton, N.J., and in a variety
of long-life odorants which lend a pleasant aroma to the space in
which the desiccant bag is located.
 The bag can be economically assembled and loaded by a known
production device called a "form, fill and seal machine."
Humidity indicator 11 is adhered to a cut flat sheet of the Tyvek
Bag material on a side which will become the bag outer surface.
The sheet is then machine folded along its length to form a tube
which is heat sealed along a side or back edge. The lower end of
the bag is similarly heat sealed, and the bag is then loaded with
desiccant material 15 following which the open upper end of the
bag is heat sealed to completely enclose the desiccant. For shipment
and storage before use, the completed bag is sealed in a foil bag
17 (FIG. 2) to be isolated from the outside environment.
 The materials used in the bag and contents are nontoxic,
and no disposal problems are presented when the indicator shows
desiccant exhaustion. The bag is easily stored, handled, and placed
in service, and provides a convenient, effective and economical
means for humidity control and prevention of condensate water in
storage areas to be protected.