August
21,
2003
1
RS­
44
Risk
Analysis
This
analysis
does
not
contain
Clean
Air
Act
(
CAA)
Confidential
Business
Information
(
CBI)
and,
therefore,
may
be
disclosed
to
the
public.

In
February
of
2001,
the
EPA
recommended
RS­
24
for
SNAP
approval
in
the
refrigeration
and
air­
conditioning
sector.
In
2003,
an
application
was
submitted
for
the
use
of
RS­
44,
which
contains
the
same
chemical
constituents
and
is
proposed
for
all
the
same
end­
uses
as
RS­
24,
excluding
motor
vehicle
air
conditioning.
RS­
44
only
varies
from
RS­
24
by
the
percentage
of
each
constituent
within
the
blend
(
Table
1).
Therefore,
in
analyzing
the
risks
associated
with
the
use
of
RS­
44,
only
the
sections
of
the
risk
screen
that
are
dependent
upon
the
percent
of
the
constituents
are
being
addressed.
These
sections
include:

 
Occupational
Exposure
and
Risk
Screening
Analysis
 
Consumer
Exposure
Analysis
 
Asphyxiation
Analysis
 
Flammability
Analysis
Table
1.
Proposed
Substitute
Blend
Refrigerant
Blend
RS­
24
RS­
44
Constituents
Percent
Composition
Occupational
Exposure
and
Risk
Screening
Analysis
Occupational
exposure
modeling
was
performed
for
the
components
of
the
proposed
blend
to
ensure
that
use
of
the
blend
does
not
pose
unacceptable
risk
to
workers.
For
each
of
RS­
44'
s
components,
in
all
proposed
end
uses
for
both
manufacture
and
disposal,
the
highest
8­
hour
estimated
exposure
was
well
below
the
component's
long­
term
exposure
threshold
(
Table
2).
Likewise,
for
each
component,
the
highest
15­
minute
estimated
exposure
was
well
below
the
component's
short­
term
exposure
threshold
(
Table
2).

The
analysis
concluded
that
occupational
exposure
to
any
of
the
constituents
in
the
RS­
44
blend,
,
is
not
expected
to
pose
unacceptable
risks
to
workers.
August
21,
2003
2
Table
2.
Occupational
Exposure
Levels
Chemical
Long­
term
Exposure
Limit
(
ppm)
Short­
term
Exposure
Limit
(
ppm)
8­
hour
TWA
(
ppm)
15­
minute
TWA
(
ppm)

Consumer
Exposure
Analysis
This
section
presents
estimates
of
potential
consumer
exposures
to
alternative
refrigerants
used
in
home
appliances.
An
assessment
of
chronic
exposure
resulting
from
routine
refrigerant
leaks
and
short­
term
exposure
resulting
from
catastrophic
leaks
are
detailed
below.

The
results
reported
in
the
Background
Document
indicate
that
for
chronic
consumer
exposures
during
leakage
and
servicing
events,
were
below
the
RfCs.
Because
of
the
conservative
nature
of
the
analysis
presented
in
the
Background
Document,
it
is
not
believed
that
servicing
equipment
containing
RS­
44
would
pose
a
significant
risk
to
consumers.

The
results
reported
in
the
Background
Document
also
indicate
that
for
short­
term
consumer
exposures
during
servicing
and
catastrophic
release
events,
the
exposure
concentrations
estimated
from
servicing
operations
involving
recycling
of
refrigerators
and
freezers,
dehumidifiers,
central
air
conditioners
or
heat
pumps
in
the
basement,
and
window
air
conditioners
are
below
the
EGLs.
Consumer
exposure
concentrations
estimated
from
accidental
releases
(
involving
release
of
the
entire
charge)
from
refrigerators
and
freezers,
dehumidifiers,
central
air
conditioners
or
heat
pumps
in
the
basement,
and
window
air
conditioners
in
a
room
were
also
below
the
EGLs.

Further
analysis
was
performed
to
examine
potential
catastrophic
releases
for
each
of
the
chemical
constituents
of
the
proposed
blend.
Exposure
concentrations
for
the
scenarios
were
calculated
using
the
box
model
described
in
the
Background
Document,
which
was
adapted
to
estimate
concentrations
on
a
minute­
by­
minute
basis.
The
analysis
was
undertaken
to
determine
the
15­
and
30­
minute
TWA
for
each
component
of
the
blend,
which
was
then
compared
to
the
cardiotoxic
NOAEL
values
to
assess
the
risk
to
consumers.

The
chemical
composition
of
the
refrigerant
in
the
form
of
a
weight
percentage
for
each
of
its
components,
the
molecular
weight
of
each
component,
the
dimensions
of
the
enclosed
space
and
the
amount
of
refrigerant
released
(
assumed
to
be
90%
of
the
charge
size)
were
used
to
calculate
August
21,
2003
3
the
concentration
of
released
refrigerant
in
the
enclosed
area.
The
room
size
and
refrigerator/
freezer
or
air
conditioning
unit
charge
size
for
each
scenario
are
as
follows:

 
Bedroom
scenario:
The
bedroom
size
was
assumed
to
be
41
m3
(
EPA
1994).
The
charge
size
for
the
window­
mounted
air
conditioning
unit
was
567
g
(
AHAM
1996).

 
Basement
scenario:
The
size
of
the
basement
was
assumed
to
be
102
m3
(
EPA
1994).
The
charge
size
for
the
central
air
conditioning
unit
was
4.5
kg
(
UNEP
TOC
1994).

Refrigerant
concentrations
were
modeled
under
two
air
change
scenarios
believed
to
represent
the
range
of
potential
flow
rates
for
a
home,
assuming
flow
rates
of
2.5
and
4.5
air
changes
per
hour
(
ACH)
(
Sheldon
1989).
Additional
simplifying
assumptions
have
been
made
for
these
calculations.
First,
the
rooms
are
assumed
to
be
empty,
with
no
cabinets,
furniture
or
fixtures.
Second,
there
is
no
applied
air
motion
(
i.
e.,
no
fan
or
motion
of
people).
Finally,
in
order
to
simulate
the
vertical
concentration
gradient
that
will
occur
because
of
the
weight
differential
between
refrigerant
and
air,
it
is
assumed
that
95
percent
of
the
leaked
refrigerant
mixes
evenly
into
the
bottom
0.4
meter
of
the
room,
and
the
rest
of
the
refrigerant
mixes
evenly
in
the
remaining
volume
(
Kataoka
1999).

The
results
of
the
modeling
indicate
that
for
all
blend
constituents,
the
estimated
15­
and
30­
minute
TWA­
predicted
exposure
concentrations
are
below
their
cardiotoxic
NOAEL/
LOAELs
(
Table
3
and
Table
4).
There
are
a
few
caveats
that
should
be
considered
when
evaluating
the
results
of
this
analysis.
In
particular,
the
analysis
does
not
consider
opened
windows,
fans
operating,
conditioned
airflow
(
either
heated
or
cooled)
and
other
variables
that
would
reduce
the
levels
to
which
individuals
would
be
exposed,
making
this
scenario
fairly
conservative.
Hence,
under
those
conditions,
it
is
believed
that
actual
exposure
levels
would
be
even
further
below
the
cardiotoxic
NOAEL/
LOAEL
for
the
15­
or
30­
minute
period.

Asphyxiation
The
risk
of
asphyxiation
for
the
chosen
"
worst­
case"
scenarios
was
investigated
for
the
RS­
44
refrigerant.
This
analysis
does
not
consider
those
conditions
that
are
likely
to
occur
that
would
reduce
the
levels
to
which
individuals
would
be
exposed,
such
as
open
doors
or
windows,
fans
operating,
conditioned
airflow
(
either
heated
or
cooled),
or
even
openings
at
the
bottom
of
doors
that
allow
air
to
flow
in
and
out.
As
such,
the
assumed
"
worst­
case"
scenario
is
highly
unlikely
and
actual
exposure
is
not
expected
to
impose
significant
risk
on
consumers.

For
the
first
scenario
(
release
from
a
window
unit
in
a
bedroom),
assuming
stratification,
the
maximum
charge
of
RS­
44
necessary
to
cause
an
oxygen
deficiency
in
air
to
16
percent
was
calculated.
This
value
is
the
minimum
guideline
for
respirator
usage
as
stated
in
OSHA
regulation
1910.134,
and
represents
seriously
impaired
coordination,
but
not
death.
Assuming
nitrogen
and
oxygen
retain
the
same
relative
volumes
in
the
rooms
with
the
balance
composed
entirely
of
RS­
44,
and
the
pressure
of
the
room
doesn't
increase
significantly
with
the
addition
of
August
21,
2003
4
the
refrigerant,
the
corresponding
maximum
charge
necessary
for
16
percent
oxygen
in
the
lower
stratum
is
2.95
kg.
The
second
scenario
(
release
from
a
central
air
conditioning
unit
in
a
basement),
the
corresponding
maximum
charge
necessary
for
16
percent
oxygen
in
the
lower
stratum
is
7.33
kg.
Charge
requirements
to
reach
the
same
effect
in
the
upper
strata
would
be
even
higher
because
of
the
larger
volumes
there.
These
values
are
significantly
larger
than
the
charges
in
the
scenarios
and
thus
represent
no
risk
of
asphyxiation
or
impaired
coordination.
Therefore,
EPA
does
not
believe
that
the
use
of
RS­
44
in
this
end­
use
poses
a
significant
risk
of
asphyxiation
to
consumers.

Flammability
Analysis
It
is
important
to
consider
the
flammability
of
substances
when
investigating
their
acceptability
for
use
as
refrigerants
since
substitutes
that
are
flammable
could
pose
safety
concerns
to
workers.

To
assess
the
flammability
of
a
gaseous
substance,
the
molecular
weight,
the
mixing
ratio,
air
exchange
rate,
and
volume
of
the
space
into
which
the
charge
is
released
is
used
to
calculate
the
instantaneous
concentration.
If
the
instantaneous
concentration
exceeds
the
lower
explosive
limit
of
the
substance,
then
it
is
considered
flammable.
This
means
that
an
ignition
source
(
e.
g.,
static
electricity,
a
spark
resulting
from
a
closing
door,
or
a
cigarette)
could
cause
an
explosion
or
a
fire
when
exposed
to
a
concentration
of
above
its
lower
explosive
limit.

The
flammability
of
,
contained
in
the
RS­
44
formulation,
was
analyzed
using
the
same
scenarios
used
for
consumer
exposure
analysis.
In
each
scenario,
it
is
assumed
that
the
entire
charge
of
RS­
44
leaks
into
the
bedroom
or
basement.
For
both
the
window
air
conditioner
in
the
bedroom
and
the
central
air
conditioner
in
the
basement,
the
instantaneous
concentrations
of
were
below
their
respective
lower
flammability
limits
(
Table
5).
Therefore,
RS­
44
is
not
considered
flammable.

Table
5:
Flammability
Instantaneous
Concentration
of
(
ppm)
Lower
Explosive
Limit
(
ppm)
Instantaneous
Concentration
of
(
ppm)
Lower
Explosive
Limit
(
ppm)

Bedroom
Basement
Conclusion
Use
of
RS­
44
is
recommended
for
SNAP
approval
in
the
refrigeration
and
air­
conditioning
sector.
Analysis
of
occupational
exposure,
consumer
exposure,
asphyxiation,
and
flammability
has
shown
that
the
use
of
RS­
44
will
not
pose
a
risk
to
human
health.
General
population
exposure
analysis
performed
in
the
RS­
24
risk
screen
indicates
that
for
the
refrigeration
and
air
conditioning
sector,
the
highest
exposure
concentrations
of
are
below
the
RfC
values.
Therefore,
RS­
44
does
not
pose
a
threat
to
the
general
population.
Additionally,
August
21,
2003
5
atmospheric
analysis
performed
in
the
RS­
24
risk
screen
showed
that
the
constituents
contained
in
RS­
44
have
global
warming
potentials,
ozone­
depleting
potentials,
and
atmospheric
lifetimes
similar
to
other
chemicals
presented
in
the
background
document.
RS­
44
does
not
pose
a
risk
to
the
environment
and
it
is
substantially
less
harmful
to
the
ozone
layer
than
the
use
of
HCFC­
22.

References
AHAM.
1996.
Household
Appliance
Industry
HFC
Consumption
Assumptions.
Association
of
Home
Appliance
Manufacturers.
Chicago.
June
3,
1996.

EPA
1994.
Significant
New
Alternatives
Policy
Technical
Background
Document:
Risk
Screen
on
the
Use
of
Substitutes
for
Class
I
Ozone­
depleting
Substances:
Refrigeration
and
Air
Conditioning.
Stratospheric
Protection
Division.
March,
1994.

Kataoka.
1999.
"
Allowable
Charge
Limit
of
Flammable
Refrigerants
and
Ventilation
Requirements."
Draft
Proposal.
O.
Kataoka/
Daikin/
Japan,
June,
1999.

UNEP
TOC.
1994.
1994
Report
of
the
UNEP
Refrigeration,
Air
Conditioning
and
Heat
Pumps
Technical
Options
Committee,
1995
Assessment.
August
21,
2003
6
Table
3.
Estimated
Short­
Term
Exposure
Levels
for
the
Components
of
RS­
44
(
Window
Unit)

Baseline
Flow
Rate
=
4.5
ACH
Baseline
Flow
Rate
=
2.5
ACH
Lower
stratum
Upper
stratum
Lower
stratum
Upper
stratum
Chemical
Cardiotoxic
NOAEL/
LOAEL
(
ppm)
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
August
21,
2003
7
Table
4.
Estimated
Levels
of
Short
Term
Consumer
Exposure
for
the
Components
of
RS­
44
(
Central
AC)

Baseline
Flow
Rate
=
4.5
ACH
Baseline
Flow
Rate
=
2.5
ACH
Lower
stratum
Upper
stratum
Lower
stratum
Upper
stratum
Chemical
Cardiotoxic
NOAEL/

LOAEL
(
ppm)
a
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
15­
minute
TWA
(
ppm)
30­
minute
TWA
(
ppm)
