LOOKING BEYOND THE OBVIOUS
BY DAVID F. PETERSON
Four years ago, on a Saturday morning in the fall, we responded to a small jewelry store in a large retail mall. Several employees were complaining of headaches and nausea.
The first-in engine crew noticed a slight, irritating odor in the 1,000-square-foot store. Interviews with employees revealed that many had been ill with flu-like symptoms all that week, yet many could not smell the odor. The engine officer called for our department`s squad, which carries the air-monitoring instruments.
Squad members identified the slight odor as that of “rotten eggs,” which could be hydrogen sulfide. After interviewing employees for specific symptoms, we began searching for the source of their illness, using an air-monitoring instrument with the capability of detecting hydrogen sulfide. The instrument never registered a reading for hydrogen sulfide.
NOT-SO-OBVIOUS SOURCE
We continued searching and entered a small room near the back of the store that contained the electrical panels and cleaning supplies. The odor was slightly more concentrated in this room. We looked through all the materials, only to come up empty-handed. The last item we checked was the auxiliary lighting system within the room. The battery for this light unit was extremely hot, and the odor was more concentrated near the ceiling of this small room. We determined that this light unit had to be the culprit!
It appears that the battery charger for this light was literally “cooking” the battery, causing it to dry up and give off gas hydrogen sulfide. To verify that hydrogen sulfide was present near this light unit, we used colorimetric indicator tubes and found .5 parts per million (ppm) of this gas. Out of curiosity, we also tested for airborne sulfuric acid and could find none. The maintenance staff quickly removed the dry battery and ventilated the store to remove the irritating odor.
Further research indicated that hydrogen sulfide exposure can irritate the eyes and cause respiratory problems, dizziness, headaches, nausea, and general fatigue. These symptoms may appear after exposure to low concentrations over a long time period. According to the 3M respirator selection guide list, the odor threshold range for this material for most people is .001 to .13 ppm. Because hydrogen reportedly causes olfactory fatigue, victims generally do not realize it is still present because they can no longer smell it.
These problems associated with hydrogen sulfide exposure were consistent with the employees` complaints. The low odor threshold also explains why we could smell this gas but not detect it with our initial air monitor. Fortunately, we had a very sensitive colorimetric tube capable of detecting hydrogen sulfide. This tool and our reasoning helped to find the source of the employees` health problems. n
“EXPLODING SUPPORTING COLUMN” POSES
HAZARD TO RESPONDERS BY RUDY RINAS
My engine company was the second-due engine to respond to a fire that occurred at 23:45 hours on February 16, 1997. We responded with Engine 46, Truck 17, Tower Ladder 34, and Battalion 23. The fire was at 96th and Clyde in Chicago. En route, Engine 46 and Truck 17 found the fire in a bowling alley at 2251 E. 95th Street. The building consisted of two sections: Section 1 was a one-story structure of ordinary construction and had a flat roof. Section 2 was of ordinary construction and contained three bowstring trusses. Light smoke was showing on arrival.
After forcing entry, it was quickly determined that the fire had advanced to a point where a defensive operation would be used. We requested a box alarm. Tower Ladder 34 was supplied with a four-inch line, and we set up a portable deluge gun in Sector 3 to protect the garages across the alley from the fire building.
After a short time, fire showed through the roof. Soon, the truss roof collapsed. This truss roof collapse was a classic in that it pushed out the rear wall the width of the alley. The intense radiant heat from the large volume of fire created after the collapse caused only paint blister damage to a few garages across the alley, due to the position of the deluge gun.
While members were working the deluge gun on the garages, a tremendous explosion from within the fire building caused everyone in our area to recoil and take cover. After the blast, a hail of pea- to half-dollar-sized pieces of metal showered the area. These pieces sizzled as they landed in the snow and water on the ground.
A few days after the fire, while walking through the fire building during a postincident analysis, I found the cause of the explosion. One of the three steel pipe columns that supported the trusses had exploded. The columns had plates welded to the top and bottom. The end of the trusses rested on the top plate. An I-beam tied the three columns together. The welding of the plates to the column created a sealed cylinder. It can only be presumed that the fire caused an increase in the internal pressure of the column until it failed with explosive force.
After 20 years in the fire service, I have seen driveshafts, shock absorbers, bumpers, and compressed gas cylinders that have exploded as a result of internal overpressures, but never building support columns.
An incident of this kind highlights the importance of knowing building construction during walk-through inspections and preplanning. The presence of a steel pipe column with welded top and bottom plates should be recognized as a cylinder with the potential to explode under fire conditions. This is an example of yet another hidden hazard faced by firefighters, even in a defensive operation mode.
As a lesson learned from the incident, I will try to position my personnel so that a protective barrier is between us and the fire building if possible. This might shield us if an explosion propels shrapnel from the fire building after a collapse resulting from an intense fire. If it`s a defensive operation anyway, there is no sense in suffering a casualty from an unexpected hidden hazard such as this one.
 |
 |
 |
(Top left and right) The remains of the support column that exploded. The columns were seamless steel pipe with plates welded to the top and bottom, such as the one in the bottom right photo. Three columns were tied together with I-beams. The ends of the trusses rested on the top plate that spanned the bowling alleys. The top plate of the column that exploded is still attached to the I-beam in the top left photo. (Photos by author.)
