Evening star., 1949-11-05
Post Office Blast Laid
To Hot Gases From
Electrical Equipment

Hot gases from overheated elec-
trical equipment acted as a giant
blow torch in the explosion and
fire at the Post Office Depart
ment Building Tuesday, an off,
cial report said today.
Fourteen persons were injured,
none seriously. and 5000 employees
were routed from the block-square
building on Pennsylvania avenue
between Twelfth and Thirteenth
streets NV, when the blast
rocked the structure.
Damage, confined largely to the
seventh and eighth floors, has been
set at $150,000 to 100000, Off
cials said today.
w. E. Reynolds, commissioner
of public buildings in the Gen.
eral Services Administration, is
sued preliminary report of the
Investigating Committee, blaming
a SRort circuit in the electric
panel on the eighth floor.
CONSTRUCTION PRACTICE.
At the time of the construction
of the building in 1934-5, it was
common practice to place trans
formers on the top floors, accord
ing to L. M. Endres, chief elec-
trical engineer for PBA. Years
prior to that date, however, saw
them in Easements.
Since then, We've changed our
ideas, particularly with the ad-
vent of air conditioning" he said.
1T is better to have the trans
formers in the basement and near
the heavy electric load such as
an air-conditioning unit would
draw. Another reason for base
ment installation is easy accessi-
bility."
The transformers were not af-
fected by either the blast or fire.
officials said and are in perfect
condition now.
Costly to Move.
Moving of the heavy equipment
to the basement would entail con-
siderable expense. Mr.. Endres
said.
The explosion and fire, he ex-
planned, was caused by a short
circuit which could not be taken
care OF by circuit breakers.
The investigation thus far.
which has brought in experts from
the Bureau Of Mines, the Bureau
OF Standards. Potomac Electric
Power Co. and the Fire Depart
ment. discloses. in official Ian
guage that:
l. The fire started in the elec-
trical distribution system from q
short circuit at the north
west corner Of the eighth floor.
2. Electrical conductors be-
tween the transformer vaults near
the northeast and northwest cor
ners became overheated.
3. Insulation of the conductors
became vaporiZed in the ducts.
The resulting gas. which is be-
lieved to be inflammable, did not
burn in the ducts because of lack
OF oxygen. but leaked out at the
pull boxes and mixed with air In
the space above the eighth-story
ceiling and the spaces over the
ceiling of the outside rooms Of
the seventh story.
4. While this was going on. the
gas escaping at the panel box,
having already ignited, was acting
as a giant blow torch.
Explosive Gas Set OF.
Arcing Of wires from which in
sulation had been burned set off
the explosive gas, blowing down
long stretches of corridor ceilings,
buckled or blew down ceilings and
ignited the termal insulation over
the corridor ceilings. the report
said.
Immediate repair work has
lights, elevators and other elec-
trical equipment back in operation
and Federal Communications
Commission employees on the two
damaged floors have either re-
turned to their Offices or been re-
located until the damage is re-
paired. Mr.. Peters said today.
Most of the damage, the pre-
liminary report said, was caused
by explosion, rather than fire. tt
lauded the prompt response" of