[labnetwork] ambient gas detection for bulkheaded tools

[John Shott]

Iulian:

Although we don't have much in the way of bulkheaded tools, I'd like to 
offer a couple of comments to the already good points made by a number 
of my respected colleagues.  In particular, like many of the other 
sites, most of our detectors are monitoring enclosed/exhausted spaces 
associated with tools, although we do tend to use a smaller number of 
"room air" detectors as something of a backup.  For example, in an aisle 
with a number of chlorine etchers, we tend to have one chlorine detector 
in each tool exhaust and then a single chlorine detector sniffing the 
room air in that aisle.

For all of this to work ... and this may depend on your local codes, but 
is certainly the rule in Santa Clara County and, I believe, throughout 
California ... the alarm limit of your detectors monitoring the 
exhausted spaces need to be set to the PEL of the gas (the requirement 
for occupied areas), rather than 1/2 IDLH (the requirement for 
unoccupied areas).  While that still may take a bit of discussion with 
your AHJ, Santa Clara County tends to be quite strict in their 
interpretations but have allowed a single detector in an exhausted space 
to do "double duty" as both monitoring for leaks in the exhausted space 
of the tool and in the nearby room area as long as the alarm limit is 
set to the PEL of that gas.  Certainly in California, code tells you 
when you need to have a detector, but does not specify where that 
detector is located.

Note: if your pump exhaust goes into this same exhaust area rather than 
to some sort of dedicated treatment system, make sure that the pump 
exhaust enters downstream of your detection point so that normal tool 
operation does not set off an alarm.

Thanks,

John


On 6/19/2013 9:53 AM, Iulian Codreanu wrote:
> Dear Colleagues,
>
> I am trying to figure out how the handle the detection of hazardous 
> gases in the ambient when part of the tool is in the chase and part in 
> the bay.  The connection between the tool and the line(s) carrying the 
> gas(es) would be in the chase so it would make sense to monitor that 
> area.  What are your thoughts on providing detectors on the bay side 
> of the wall as well?
>
> Thank you very much for your help.
>
> Iulian