Vent-Free Gas Products Industry
Explanation of
Functioning of the ODS Safety Pilot at High Altitudes
The ODS, oxygen detection safety pilot, by
design is sensitive to fluctuations in oxygen supply, and is
required to automatically activate the automatic gas valve to
shut off the unit should the oxygen level drop to a safe level
of 18% from an optimal level of 21%. Oxygen content is reduced
at “higher altitudes” and therefore the ODS safety pilot is more
likely to activate as altitude increases, potentially creating a
nuisance outage problem, but never a safety hazard as it is
“failing in the safe mode”.
Years ago the industry conducted a variety of
product performance tests at various altitudes and selected 4500
feet above sea level as the highest altitude at which ODS pilot
outage could be assured not to be a problem relative to
elevation. However during these tests, it was demonstrated that
many units in many applications operated with minimal or no
significant difficulty at elevations as high as 6000 feet. The
contributing variables can include other household appliances
such as range hoods in operation, number of people in the
home at a given time, adequacy of general household
ventilation, exposure of the pilot to drafts, ceiling fans etc.
While 4500 feet remains the recommended
maximum elevation for general consumer direction, many
manufacturers have determined that this recommendation is
extremely conservative vs. “real world” experience by
consumers. As a result, many vent-free gas products are offered
for sale in higher elevation trade areas with the understanding
that most applications will not experience nuisance outage to
the extent that the consumer wants to remove the installation.
If the problem is only occasional, most consumers are satisfied
with waiting a few minutes for adequate oxygen to re-establish,
or removing another depleting source, and then relighting the
unit. Should the consumer experience a significant problem
with pilot outage, a high altitude orifice can be ordered.
