W:\ELECTRICAL\INSTRUCT\FURNACE\FURNACE GENERAL INSTRUCTIONS 2011.DOC
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8-6 INADEQUATE VENTILATION SYMPTOMS
Vapor explosions often occur some time after ventilation becomes inadequate.
Investigate the following symptoms and take corrective action immediately:
a. A cold exhaust duct or stack while the furnace is operating usually indicates
reversal of flow in the stack.
b. Evidence of negative pressure in the furnace room, with respect to adjoining rooms
and outdoors when the door to furnace room is opened, may indicate inadequate
safety ventilation and sometimes reversal of airflow in the exhaust stack.
c. A record of fires or puffs from work in a particular furnace may indicate inadequate
safety ventilation, dangerously high vapor concentrations, the probability of an
eventual serious furnace explosion.
d. A record of work leaving the furnace with incomplete processing or unusual surface
condition may be an indication of inadequate safety ventilation.
e. Heavy deposits of condensed vapors at the exhaust stack outlet may indicate that
interior fouling has dangerously reduced the safety ventilation.
f. Deposits around furnace door cracks may indicate higher pressure inside the
furnace than in the furnace room, and a lack of positive safety ventilation.
