[TheForge] carbon monoxide

Tue Nov 12 08:56:01 2002

Wayne,

This is what MSDS's are for.  Anytime you have a question like this, =
consult an MSDS.

According to an MSDS for carbon monoxide from BOC gases
www.mwsc.com/MSDS/8.PDF=20

PEL-OSHA is 50 ppm TWA
TLV-ACGIH is 25 ppm TWA
LC50 is 1807 ppm/4 h (rat)

Starting with the last, that's the "concentration lethal  to 50% of test =
rats".  If you happen to be a rat, then you can expect 1807 ppm to have a =
50% chance of killing you outright in four hours.

The top figure is the "Permissible Exposure Limit from the Occupational =
Health and Safety Administration," namely a "time-weighted average" of 50 =
ppm.  The time period is not stated here, but typically it's "one shift" =
or eight hours.  If you were exposed to 50 ppm continuously for eight =
hours (and then NOT exposed), OSHA wouldn't object.  (OSHA hates it when =
people die on the job!  It makes so much extra paperwork for them!)   TWA, =
however, allows you to be briefly exposed to higher levels, as long as the =
normal exposure is less.

ACGIH is the American Conference of Governmental Industrial Hygienists, =
Inc., a non-governmental organization.  The following website below =
provides a definition of TLV:
http://www.ilpi.com/msds/ref/index.html

          "Threshold Limit Values (TLV's) are guidelines (not standards) =
prepared by the American Conference of Governmental industrial Hygienists, =
Inc
          (ACGIH) to assist industrial hygienists in making decisions =
regarding safe levels of exposure to various hazards found in the =
workplace.

         " A TLV=AE reflects the level of exposure that the typical worker =
can experience without an unreasonable risk of disease or injury. TLVs=AE =
are not
          quantitative estimates of risk at different exposure levels or =
by different routes of exposure."

I would conclude that 40-50 ppm is not enough to cause you injury, but =
that you wouldn't want the level to go any higher.  It would be a good =
idea to try to get it down to about 25 ppm.

However, to REALLY know what the level is, you must first calibrate the CO =
detector.  Maybe it's already in calibration, maybe not.  I have no good =
suggestions how to do this.  In industry it would be done from a source of =
known CO level, such as a gas mixture.  Such a mixture is likely to be =
above your budget.  The best bet is to contact the manufacturer and tell =
them you're getting high readings (50 ppm) near a combustion source and =
want to make sure the detector is working properly before you worry about =
fixing a problem with th source.  They may have an answer for you.

Hope this helps,

Bruce
NJ

>>> [email protected] 11/09/02 02:02PM >>>
Hello=20

  I bought a CO/propane detector for my shop as I have
  done all the plumbing myself and wanted to make sure
  I don't have any leaks, etc.  Install has gone fine,
  but now that I have a CO detector I can monitor the
  amount of CO produced by my propane forge.  When it
  comes up to temperature the monitor registers about
  40-50 PPM. I am sure it would keep climbing but I
  open a couple windows, put a fan in for exhaust
  and clear it out.

  My question is: do you all think the forge is tuned
  properly?  Are those kind of readings appropriate?
  What is a good way to vent a forge?
 =20
--=20
Wayne   =20
Hesperus, CO                    =20

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