An HVACR technician is exposed to many personal safety hazards
during the course of a normal workday. In addition to the obvious
hazards such as sharp metal, electrical wiring and climbing ladders,
the technician needs to be aware of the safety hazards that refrigerants
Refrigerant safety is straightforward: If the
refrigerant stays contained in the cylinder or in the system then
it presents little
danger to people. The hazard occurs when the refrigerant comes
out of the container or system, often quickly and unexpectedly.
Injuries can be avoided if regular safety checks are performed.
Regular checks on containers and systems for holding pressure,
and preparing safety equipment and procedures to minimize personal
exposure after unexpected releases should help avoid any injuries
when handling refrigerants.
Specific hazards from refrigerant fall into three
Toxicity and personal exposure
Most refrigerants have undergone extensive toxicity testing before
being released for general refrigeration or air conditioning
use. Testing generally involves a range of exposure levels and
times to determine any possible effects on test animals.
• Short term exposures at high concentrations indicate any
acute hazards such as irritation,
sensitization of the heart or
and lethal concentration (LC50 is the amount which kills half
animals in a short amount of time).
• Tests that expose animals for longer periods of time, such as
90 days to two years, are designed to
indicate chronic problems.
These can include mutagenicity (changes to cells), reproductive
effects on organs or carcinogenicity (cancer-causing).
ASHRAE Standard 34* provides a safety classification for refrigerants
based on information related to
personal exposure. ASHRAE Standard
15** uses this safety rating and additional toxicity information
set requirements for machinery rooms and
sets limits on the amount of refrigerant allowed in systems
outside machinery rooms.
Many blends containing these individual components are also classified.
Refrigerants not classified in ASHRAE Standard 34 should be
reviewed with suppliers to make sure enough is known about their
toxicity properties. Some blends may not be classified, but contain
classified components. (Note: Many building codes have adopted
the newer refrigerants listed in ASHRAE standards. Some building
codes have not, and therefore, require special permits. A refrigerant
that's not listed most likely will require an engineering study
to determine if it can be used safely.)
Exposure levels are values given to refrigerants to indicate
how much of the chemical a person can regularly be exposed to
without adverse effects. All toxicity test results are considered
when setting this level. The American Conference of Government
and Industrial Hygienists (ACGIH) sets the TLV-TWA values for
chemicals. TLV-TWA stands for Threshold Limit Value-Time Weighted
Average, which is the amount of chemical a person can be exposed
to for 8 hours a day, 40 hours a week, without adverse effects.
The maximum value for any chemical is 1,000 ppm, though many
refrigerants have shown no effects in toxicity testing at values
much higher than that. Other organizations and chemical producers
have similar exposure level indexes based on the same criteria.
These are the Workplace Environmental Exposure Limit (WEEL) set
by the American Industrial Hygiene Association (AIHA); Permissible
Exposure Limit (PEL) set by OSHA; and Acceptable Exposure Limit
(AEL) used by DuPont.
There are also the Short Tenn Exposure Limit (STEL), which is
based on a 15-minute exposure time in any given day as well as
the value Immediately Dangerous to Life or Health (IDLH). These
are used to give guidance for machinery room requirements, ventilation
and alarms in an emergency or escape situation, or in circumstances
where short releases of refrigerant are expected, which could
include refrigerant transfers or servicing large equipment.
Toxicity data is usually summarized in great detail on Material
Safety Data Sheets (MSDS). What all of this data means to the
technician, however, is that commercial refrigerants are safe
enough to use provided you don't breathe too much of them. Industry
practices for handling refrigerant are intended to minimize personal
exposure as well as reduce releases into the atmosphere.
General rules to follow are:
• Minimize the amount of refrigerant released. Proper recovery
procedures, including clearing hoses, will
keep the refrigerant
in the containers instead of potentially exposing it to people.
• Never intentionally release refrigerant in a confined space.
Even the safest refrigerant can still displace
to cause suffocation.
• Set up ventilation equipment, like a portable fan, in areas where
possible release would mean high
• Refer to ASHRAE Standard 15 and local building codes for additional
If someone is exposed to refrigerant get him to fresh air, give
oxygen if needed, and get him checked by a doctor.
Flammable refrigerants present an immediate danger when released
into the air. The refrigerant can combine with air at atmospheric
pressure and ignite, causing a flame and possibly an explosion
to occur. Because of the obvious hazards, the use of flammable
refrigerants is restricted to controlled environments that
have monitors, proper ventilation, explosion-proof equipment
and generally few people near the equipment (refineries, storage
warehouses, breweries, etc.).
Some refrigerants can burn with oxygen, but only
at higher pressures or temperatures and never in air at atmospheric
are called "combustible" refrigerants. Underwriter's
Laboratories (UL) lists these refrigerants as "Practically
R-22 and R-134a fall into this category. R-22 was found to cause
a combustion hazard during a pressurized leak test with air.
For this reason, most refrigerants should be used only with pressurized
nitrogen for leak testing. As long as refrigerant is not mixed
with large amounts of air, there should be little hazard from
these refrigerants during normal handling and use.
Decomposition can occur with any refrigerant when
it gets hot enough (generally above 700° F). Refrigerant
can decompose in systems or containers exposed to fire or other
electrical shorts (burnouts), or in refrigerant lines being
soldered or brazed without being cleared first. Obviously,
containers or charged systems should never intentionally be
exposed to a flame or torch.
When a refrigerant is decomposed or burned, the primary products
formed are acids: Hydrochloric acid (HCI), if the refrigerant
contains chlorine, and hydrofluoric acid (HF), if it contains
fluorine. These products are certainly formed when hydrogen is
present, such as from the breakdown of oil, water or if the refrigerant
has hydrogen attached (like R-22 or R-134a). If oxygen also is
present (from air or water), then it's possible to form carbon
monoxide, carbon dioxide and various unsaturated carbonyl compounds
-- the most notorious of which is phosgene.
Being extremely toxic in small amounts, phosgene formation was
a real concern when traditional refrigerants (R11, R- 12, R-
113, R- 114) decomposed. Phosgene contains two chlorine atoms
and an oxygen atom. It will only form when oxygen is present
and only the refrigerants with chlorine attached will produce
phosgene (not HFCs). R22 has only one chlorine atom per molecule,
so it is extremely difficult, chemically speaking, to get another
one attached to form phosgene. Decomposition of R-22 or HFCs
may form other carbonyl fluorides, however they are not as toxic
The standard practice for handling decomposed refrigerant is
to collect the gas, treat the refrigerant and/or the system for
acid contamination, and appropriately dispose of the burnt gas.
Please note that any cylinder or system component exposed to
high heat or fire should be retested or discarded. Cylinders
used to recover burnt gas should be checked and cleaned before
being put back into service, especially the valve and/or pressure
The fact that it's a liquified gas under pressure is one of the
more obvious hazards of refrigerant. Sudden, unexpected release
of pressurized refrigerant can result in personal injury.
Refrigerant tubing, hoses, system components and some refrigerant
cylinders surely would fail at some elevated pressure without
certain safety provisions. Various pressure relief devices are
used to lower the pressure back to safe limits by releasing some
or all of the refrigerant.
Valves on many refrigerant cylinders are fitted with spring-loaded
pressure relief valves. These are typically set to release pressure
somewhere above typical refrigerant pressures at normal use or
transportation temperatures, but below the maximum service pressure
of the cylinder. When the pressure is reduced to a safe level
the valve should close itself.
Other cylinders or storage vessels are fitted with burst discs
as the pressure relief device. These are pieces of metal designed
to break at some preset pressure, again lower than the maximum
service pressure of the container. In the case of a burst disc,
the entire contents of the container will be released. This is
also the case with a fusible plug, which is designed to melt
at a certain temperature. It's used to relieve the pressure in
a tank or system in a fire situation before the pressure gets
high enough to burst the tank, tubing or system component.
Damaged or weakened refrigerant cylinders or system components
may fail at pressures lower than originally specified. Physical
abuse such as dents, scratches, rust, bulges or exposure to excessive
heat can reduce the strength of joints or the metal itself. Materials
originally designed to hold hundreds or thousands of psi pressure
might now fail at typical refrigerant pressures. In the case
of damaged cylinders, the pressure relief device shouldn't be
relied upon for protection; the cylinder should be repaired and
retested or discarded.
The best way to avoid pressure-related hazards is to always
use cylinders and system components that have the correct pressure
rating for the refrigerant you're using. Table 1 lists the typical
cylinder service pressures that manufacturers and distributors
use for various refrigerants. Pressure ratings for system components
must be chosen based on the application and expected service
pressures for the intended application. Pressure ratings are
also based on the refrigerant chosen. Always check for signs
of damage or excessive wear before filling recovery cylinders,
picking up new refrigerant cylinders or attaching new parts to