The document discusses industrial ovens and furnaces used in various industries. It describes different types including dryers, baking ovens, kilns, furnaces, autoclaves, and thermal oxidizers. It discusses important design considerations for these industrial heating devices including housing construction, ventilation, fire protection, heating systems, controls, and operational support. Proper design and operation is important to prevent fires and explosions from occurring in industrial ovens and furnaces.

1. Fires and Explosions in
Ovens and Furnaces
By: John Holecek

2. What are Industrial Ovens and Furnaces?
• We are not talking about home cooking and home heating
systems.
• The terms oven, furnace, and kiln are used somewhat
interchangeably. Often vary as much by industry than
inherent differences in design.
• The range of ovens, furnaces and applied heat transfer devices
used in industry is quite large.
• Lets look at some examples.

3. Dryers
• Dryers are used to evaporate a liquid, often water, from
a product.
Dry Kiln’s are used to dry water
and volatiles from green lumber.
Grain dryers are used to dry
grain before storage.

4. Baking Oven
• Baking Ovens are used to heat products and thereby cause a
physical change in the product. They will also dry products.
Paint Baking ovens cure coatings
by a heat catalyzed chemical
reaction.
Food Baking Ovens are used to
cook foods such as chicken and
bread.

5. Kilns
• Kilns are essentially high temperature ovens, usually
operating at 1000ºF+.
Brick Kilns are used to fire bricks,
typically at approximately 2500F.
Rotary lime kilns create lime from
limestone by a heat catalyzed
chemical reaction.

6. Furnaces
• Furnaces are also used to heat products, often at higher
temperatures, and thereby cause a physical change in the
product.
Heat treating furnaces change the
properties of metal.
Furnaces come in many different
sizes, from small units shown above
to large units as shown on the left.

7. Autoclaves
• Autoclaves: Ovens that operate at substantially non-
atmospheric pressures either pressurized or at vacuum. They
may also have specially constituted atmospheres.

8. Thermal Oxidizers
• Thermal oxidizers: Used to thermally incinerate undesireable or
hazardous compounds into less problematic components. May also
use catalysts to assist in breaking down the compounds.

9. Other Heating Devices
• Many applied heat transfer machines use some of the
same design elements as industrial ovens.
Thermal oil heaters. Heated parts washers share some
safety design elements with ovens.

10. Other Heating Devices
Thermal Oxidizer
Water Heater
Biomass Fired Boiler

11. What types of losses occur with ovens and furnaces?
Explosions:
• From fuel supply
• From product being processed
Fires:
• From product being processed
• From combustible residues
Worker’s Compensation:
• Injuries from fires and explosions
• Electrocutions
• Burns from hot surfaces
Loss of Business Income
Failure to Perform

12. What defines the correct way to design, build, and
operate ovens and furnaces?
• Codes and Standards:
Codes have been written in a format suitable for adoption into law
independent of other codes and standards. An example is the
International Fire Code.
Standards are documents containing mandatory provisions using the
word “shall” to indicate a requirement. They are written in a form
such that their provisions become mandatory when referenced by
another code or standard. An example is NPFA 86: Standard for
Ovens and Furnaces.
• Good Engineering Practice
• Design Guides
• Normal Practices / State of the Art

13. Codes and Standards that directly reference oven
design:
• International Fire Code (IFC):
Has a whole chapter on industrial
ovens. Incorporates compliance
with NFPA 86 by reference. The
IFC is legally adopted in 42 states.
• NPFA 86: Standard for Ovens and
Furnaces: The “textbook” of safe
oven design.
• NFPA 13: Standard for the
Installation of Sprinkler Systems:
Gives information on installing
sprinklers in ovens.

14. Other codes, standards and guides that relate to safe
oven design:
• NFPA 54, National Fuel Gas Code, Gives proper
methods for fuel gas piping.
• NFPA 31, Standard for the Installation of Oil-
Burning Equipment, Gives proper methods for
fuel oil piping.
• NFPA 58, Liquefied Petroleum Gas Code, Gives
proper methods for
storage, handling, transportation, and use of
LP-Gas
• NFPA 70, National Electrical Code®, Gives
proper methods for electrical wiring of ovens.
• NFPA 91, Standard for Exhaust Systems for Air
Conveying of Vapors, Gases, Mists, and
Noncombustible Particulate Solids, Gives proper
methods of exhausting ovens.
• NFPA 68, Guide for Venting of
Deflagrations, Gives proper methods for
explosion venting.
• FM Data sheet 6-9: gives excellent guidance on
the proper design of ovens.

15. What are the requirements for permitting ovens and
furnaces?
• Requirements vary by location.
Different states, counties, and cities
can have different requirements.
• Where the International Fire Code is
enforced, fire code officials are
“authorized” to require building and
operational permits for installing or
operating an industrial oven.
• Most states issue specific
modifications to the IFC which may
define if permits for ovens are
required or may give discretion to
the permitting official.

16. Ovens are separated by class (per NFPA 86):
Class A Furnace. An oven or furnace that has heat utilization equipment
operating at approximately atmospheric pressure wherein there is a
potential explosion or fire hazard that could be occasioned by the presence
of flammable volatiles or combustible materials processed or heated in the
furnace.
(Translation) Ovens that are not under pressure or vacuum and process
combustible products or dry / cure flammable coatings. Examples: Many
paint baking ovens, lumber kilns.
Class B Furnace. An oven or furnace that has heat utilization equipment
operating at approximately atmospheric pressure wherein there are no
flammable volatiles or combustible materials being heated.
(Translation) Ovens that are not under pressure or vacuum and process
noncombustible products and do not dry / cure flammable coatings.
Examples: Brick kilns, lime kilns, dryers for non flammable liquids on non
combustible products

17. More oven classifications:
Class C Furnace. An oven or furnace that has a potential hazard due
to a flammable or other special atmosphere being used for treatment of
material in process.
(Translation) Ovens and furnaces with potentially flammable or hazardous
atmospheres. Example: Metal heat treating ovens
with flammable gas atmospheres, integral quench furnaces and molten salt
bath furnaces
Class D Furnace. An oven or furnace that operates at temperatures above
ambient to over 5000°F (2760°C) and at pressures from vacuum to several
atmospheres during heating using any type
of heating system. These furnaces can include the use of special processing
atmospheres.
(Translation) Ovens that operate under substantial vacuum or pressure.
Example: Autoclaves for curing composite materials.

18. Design Requirements
We will look at the following elements of oven design:
• Housing Construction and Ductwork
• Ventilation
• Fire Protection
• Heating Systems
• Control Systems
• Operational Support

19. Housing Construction
• Noncombustible housing materials
required
– No wooden structures
– No plastic foam insulation
• Provide clearance to combustible
surroundings
– Keep adjacent materials below 160F
• Must provide clearance on all sides
and adequate maintenance access
• Class D ovens with pressurized
housings above 15psi must be
designed to the ASME Boiler and
Pressure Vessel Code

20. Housing Construction
Explosion Relief: Specially designed provisions that allow for
freely relieving internal explosion pressures. Prevents an
exploding oven from becoming a giant hand grenade.
Required on all fuel fired ovens with the following exceptions:
– Indirect fired ovens with demonstrated low levels of
combustible / flammable vapors
– Class D ovens (Autoclaves) or Thermal Oxidizers
– Certain high temperature furnaces that are made of
minimum 3/16” thick steel, structurally reinforced, and
refractory lined.
– Certain low oxygen type furnaces

21. Housing Construction
• Explosion Relief:
– 1 ft2 of relief area is required for every 15 ft3
of oven volume
– Often explosion relief is accomplished by
leaving some roof panels simply laid in
place without significant restraint
– Openings, and doors with listed hardware
are included in the relief area
– Basis of design should be that panels relieve
explosive pressure before the oven’s safe
design internal pressure limit is exceeded
– Heavy materials should not be placed on
relief panels
– Extensions to the oven such as heater
houses and ductwork should be included in
the oven volume amount when calculating
relief area

22. Ductwork
• Ducts must be made of noncombustible
materials
• Include provisions for cleaning out ducts,
especially when products generate combustible
dusts or residues. Generally this requires clean
out doors.
• Guard or insulate surfaces over 160F.
• When vapors are likely to have heavy
concentrations of condensable gasses, the duct
should be insulated. Otherwise a heavy
buildup of combustible residue will form in the
duct and present a fire hazard.
• Keep hot surfaces of ducts away from
combustible surroundings. This is frequently
improperly done at the exhaust duct
penetration through the building roof.
• NFPA 91, Standard for Exhaust Systems for Air
Conveying of Vapors, Gases, Mists, and
Noncombustible Particulate Solids, has additional
requirements

23. An example of a correct penetration of an exhaust duct
through a building roof
Duct
Bar Joists
Rain Skirt
Air Gap Per Code
Combustible Roof
Material
Steel
Support

24. Fire Protection
Ovens and furnaces are frequently equipped with fire
protection systems. These systems include wet pipe, dry
pipe, deluge systems. Some ovens are installed with
special fire protection such as Clean Agent or Water Mist
systems. The most common practice is to install a wet
pipe system with the supply piping located outside the
oven.
The International Fire Code and NFPA 86 currently differ
somewhat in the requirements for fire protection systems.
Let’s look at what they say.

25. 2012 International Fire Code on Oven Fire Protection
SECTION 2106
FIRE PROTECTION
2106.1 Required protection. Class A and B ovens which contain,
or are utilized for the processing of, combustible materials
shall be protected by an approved automatic fire-extinguishing
system complying with Chapter 9.
2106.2 Fixed fire-extinguishing systems. Fixed fire-extinguishing
systems shall be provided for Class C or D ovens to
protect against such hazards as overheating, spillage of molten
salts or metals, quench tanks, ignition of hydraulic oil and escape
of fuel. It shall be the user’s responsibility to consult with
the fire code official concerning the necessary requirements for
such protection.

26. 2012 International Fire Code
Clearly, The International Fire Code often
requires that industrial ovens be equipped with
fire protection systems.
Let’s see what NFPA 86 has to say about fire
protection in industrial ovens.

27. NFPA 86 (2011)– Fire Protection System Requirements
“A study shall be conducted to determine the need for fixed or portable fire protection systems for
ovens, furnaces, or related equipment. This determination of the need for fire protection systems
shall be based on a review of the fire hazards associated with the equipment. Where determined to
be necessary, fixed or portable fire protection systems shall be provided. “
The Explanatory material in Appendix A of the Standard does attempt to clarify things:
“Automatic sprinkler protection should be considered for ovens, furnaces, or related equipment if
any of the following conditions exists:
(1) The material being processed is combustible.
(2) Racks, trays, spacers, or containers are combustible.
(3) If there are areas where appreciable accumulations of combustible drippings or deposits are
present on the inside of the oven surface or on racks, trays, and so forth.
The type of sprinklers and arrangement should be appropriate to the oven arrangement, interior
ductwork, and the material passing through the oven.
Note: Past versions of NFPA 86 required fire protection in ovens
processing combustible materials.

28. Wet Pipe System
Wet pipe sprinklers systems are the most
common type of fire protection installed in
industrial ovens. High temperature heads are
typically rated 50F above the high temperature
limit setting for the oven.
As stated in the appendix of NFPA 13, Standard
for the Installation of Sprinkler Systems:
“The preferred arrangement for piping is outside of
the oven; the sprinkler should be installed in the
pendent position. The sprinkler temperature rating
should be at least 50°F (28°C) greater than the high-
temperature limit setting of the oven or applicable
zone. As a minimum, the sprinkler system inside the
oven or furnace should be designed to provide 15 psi
(1 bar) with all sprinklers operating inside the
oven/furnace. Sprinkler spacing on each branch line
should not exceed 12 ft (3.7 m).”

29. Specialized Systems
• Deluge Systems : Open heads are positioned in the oven.
Water is supplied by a valve in response to actuation of spark, flame or
temperature sensors mounted in the oven or ducts.
• Steam Suppression Systems: Specialized approach that is seldom used
and actually discouraged in NFPA 86. Care must be taken to contain
steam in the oven. Steam can burn persons near oven openings.
• Water Mist Fire Protection Systems: Essentially, a deluge system
operating at high pressure with small, strategically located nozzles. The
water mist created by higher pressures control or extinguish fires by
cooling of the flame and fire plume, oxygen displacement by water
vapor, and radiant heat attenuation. Used when fast suppression is
desired and large volumes of water may be problematic.
• Dry Chemical or CO2 Systems: Specialized systems used where the
introduction of water cannot be allowed. For example, an oven used in
the manufacture of products containing reactive metals like lithium or
sodium.

30. Ventilation
• A cornerstone safety design concept for industrial ovens is that
fresh air ventilation keeps the levels of flammable or
combustible constituents below levels that can cause an
explosion.
• In fact, NFPA 86 stipulates that four times the minimal level of
ventilation be present. This should maintain a 4 to 1 safety
factor against explosive atmospheres.
 In many systems, solvents may not be
released in a uniform manner. The
way in which products are loaded
may produce peak solvent levels far
above the time weighted average.
This must be verified, especially for
batch processing type ovens.

31. Proper Ventilation Design
• Required fresh air supply rate =
– 12,000 cubic feet of fresh air for every gallon of solvent evaporated
– Plus volume of products of combustion released into the oven
• The above is the common and simple calculation for the volume of
fresh dilution air. It has been calculated using common solvents.
• The volume can be calculated in a more involved manner that uses
the specific properties of the actual volatiles in use.
• It’s very important to remember that every oven has a design basis
for the amount of volatiles released per unit of time. If the oven is
loaded in a manner that overwhelms the safety factor, an explosive
environment may result.
• Any dampers in the exhaust or fresh air ductwork must be made so
that even when closed they will pass the required safe amounts of
airflow.

32. Proper Ventilation Design
• The exhaust rate for the oven is based on the fresh air supply rate. They
are equal on a pound per minute basis. However, because air expands as it
heats, the volumetric flow rate of the exhaust fan must be corrected for the
temperature of the oven. For example: at 600F the exhaust fan rating must
be 2 times the desired fresh air supply rate.
Temp Temp Factor Temp Temp Factor Temp Temp Factor
°F °C °F °C °F °C
70 21 1 300 149 1.43 950 510 2.66
100 38 1.06 350 177 1.53 1000 538 2.75
110 43 1.075 400 204 1.62 1050 566 2.85
120 49 1.09 450 232 1.72 1100 593 2.94
130 54 1.11 500 260 1.81 1150 621 3.04
140 60 1.13 550 288 1.9 1200 649 3.13
150 66 1.15 600 316 2 1250 677 3.23
175 79 1.2 650 343 2.09 1300 704 3.32
200 93 1.24 700 371 2.19 1350 732 3.42
225 107 1.29 750 399 2.28 1400 760 3.51
Table 9.2.5.1 Temperature–Volume Conversion Table (at Sea Level)

33. Improper Ventilation Design
The designs shown lack
dedicated exhaust fans
and are not compliant
with NFPA 86.

34. Proper Ventilation Design
The designs shown are
compliant with NFPA 86.

35. High LEL Systems
NFPA 86 does allow designing up to 50% of the LEL:
“Where a continuous solvent vapor indicator and controller is provided it
(oven safety ventilation) shall prevent the vapor concentration from
exceeding 50 percent of the LEL.”
This is typically used in conjunction with air pollution control
systems. The level of solvents in the exhaust air is elevated prior to
delivery to a thermal oxidizer or concentrator / absorber.

36. Oven Heating Systems
• Ovens may be heated using any of several energy
sources:
– Fuel Gas (Typically Natural Gas or Propane)
– Fuel Oil
– Electricity
– Hot Water
– Steam
– Thermal Oil
– Hot Air from Recovered Heat
• Each heating method has its own requirements.

37. Oven Heating Systems
• All systems need to accomplish the following in a safe
manner:
– Allow stopping and starting the supply of energy to
the oven in a safe manner.
– Keeping the energy source flow rate within safe
limits.
– Have provisions that allow interlocking of the oven’s
safety controls to the operation of the energy source.
– Have appropriate maintenance provisions

38. Fuel Gas System
• Photograph of fuel gas piping manifold with
combustion air blower.

39. Fuel Gas System
• NFPA Diagram of fuel gas piping manifold

40. Infrared Fuel Gas Fired System
Fuel gasses can also be
used to fire infrared heating
burners. These systems
typically premix gas and air
in the proper ratio. The
gas / air mixture is piped to
the burners.

41. Fuel Oil System
• Photograph of fuel oil piping manifold

42. Fuel Oil System
Diagram of fuel oil piping manifold

43. Electrically Heated System
Electric Infrared Oven with Conveyor

44. Electrically Heated System
• Use any of several types of
resistance electrical elements to
provide heating capacity.
• Convective Heating Elements:
Essentially, like the heating elements
in a home oven. Generally used to
supply convective heat to an oven.
• Radiant Elements: Lamps in any of
several shapes that operate at high
element temperatures and supply a
significant part of their energy as
thermal radiation.

45. Fluid Heated Systems
• These systems use a flow of a hot fluid
through a heat exchanger to supply
energy to the oven. This includes hot
water, thermal heat transfer fluids
(thermal oil), and steam (not actually a
fluid). NFPA 86 has requirements for
fluid heated systems including:
• Piping per ASME B31.1, Power Piping.
• Insulation requirements for thermal oil.
• Isolation valve requirements.
• Locations and filtration requirements
for heat exchangers.

46. Steam Heated System
• Uses a flow of steam through a steam to air
heat exchanger to provide heat for the oven.
Typically used on lower temperature ovens.
Requires a steam boiler which often supplies
steam to several heated devices.

47. Hot Water Heated System
• Uses a flow of hot water through a water to air heat exchanger
to provide heat for the oven. Typically used on lower
temperature ovens. Requires a hot water boiler and a pumping
circuit which often supplies water to several heated devices.

48. Hot Oil Heated System
• Uses a flow of hot oil (thermal heat transfer fluid) through a liquid to air
heat exchanger to provide heat for the oven. Requires a thermal oil heater
which normally supplies hot oil to several heated devices. Often used in
plants that use waste for firing the heaters. Thermal oil heated systems
often are designed with the oil temperature near or above the auto-
ignition temperature of the oil in air. Extreme care must be taken to avoid
leaks as a leak can easily cause a fire.

49. Recovered Energy Heated System
• Uses energy recovered from a higher temperature process to
supply heat to the oven. This can take many forms. One
example is to recover energy from an oxidizer and use it to
preheat the fresh air supply to an oven. Typically uses a heat
exchanger to recover the energy.

50. Oven Control Systems
• All ovens have electrical control systems that, when properly
executed and maintained, enforce the required safe logic of
operation. This logic serves to verify safe ventilation, safe
fuel conditions, and to prevent excessive operational
temperatures. Additionally, the control system may interface
to fire protection systems and material handling systems.

51. Oven Control Systems: Programmable Logic Controllers
• Many newer ovens are
controlled by Programmable
Logic Controllers (PLC’s).
NFPA 86 includes rules for
using PLC’s with ovens.
Generally, PLC’s can initiate
actions (start and stop fans
and burners) and monitor
safety controls; however,
they are not allowed to
actually process the safety
logic. Unless listed for
combustion safety service.

52. Oven Control Systems: Data Aquisition
• Some ovens are equipped with data
acquisition systems. These are often
used for quality control purposes to
record the oven temperature and
other critical variables. Many PLC
controlled systems have data
acquisition systems. In the event of a
fire or explosion, these systems can
often provide valuable data to help in
understanding the conditions at the
time of the event. Securing any such
data should be a top priority when
investigating oven and furnace
losses.

53. Ventilation Interlocks
• Fans are used to circulate
air inside ovens, to supply
fresh air to ovens and to
exhaust air from ovens.
The proper use of fans in
all of these applications is
critical to the safe
operation of the oven.

54. Ventilation Interlocks
• The fan’s motor is typically started and
stopped using a motor starter. A motor
starter is simply an electrical switch
that can be turned on and off by an
electrical signal. The starter should
include an auxiliary contact that is
wired back to the control logic. Closing
of this auxiliary contact upon giving a
“fan start” signal proves that the motor
starter switch closed and therefore the
fan motor should be energized.
However, that does not prove the fan is
actually turning and moving air.
Perhaps the V-belts between the motor
and fan are broken. An additional
interlock is required.

55. Ventilation Interlocks
• Air flow or pressure switches are used to
prove that fans are actually running and
moving air. Air flow switches are “sail
switches” that have move and close an
electrical switch due to the passage of a
minimum amount of air flow. They are
not used very much in industrial ovens.
• Typically, air pressure switches are used.
These devices are made of a small switch
attached to a flexible diaphragm. Each
side of the diaphragm is connected via
tubing to an appropriate point in the
system ductwork so that when the fan
moves air, the diaphragm flexes and
actuates the switch .

56. Ventilation Interlocks
• Air pressure switch location and operation are often
poorly designed and a misused element of safe oven
design.
• The switches are typically piped to the inlet and outlet of the
fan. This is acceptable as long as there are no mechanical
elements such as a damper that can reduce the airflow to an
level below the minimum design level. An alternate
approach is to include a fixed orifice in the duct an have the
switch sense the pressure drop across the orifice. This
actually verifies system airflow, not just a pressure difference
across a fan.

57. Ventilation Interlocks
– The pressures that are sensed by air flow
switches are low, often less than 1/25 of a
pound per square inch. Pressures this low
can be difficult to sense. Sometimes the
switch adjustment or location of the tubing
taps in the ducts make the switch’s
operation erratic. This will shut down the
oven and create a real problem for
maintenance personnel. Not
infrequently, these switches are bypassed
(jumped) to get rid of this nuisance
problem. If the fan then fails (eg, broken
belts), there will be no safety ventilation and
the control system will not sense this fact.
An explosion could be the result.

58. Purging
– Explosions have resulted from accumulations of
flammable vapors inside ovens which accumulated
when the oven was not operating. These vapors
may come from leaking fuel gas valves or from
some process related source. To prevent an
explosion of these vapors, ovens are purged prior
to attempting to light the burner(s). Purging
consists of starting all the fans and running the fans
for a timed period prior to allowing an attempt at
burner ignition. The NFPA 86 standard requires
purging four oven volumes worth of fresh supply
air prior to allowing a trial for ignition. On most
systems, one main gas valve must be proved closed
during purging by a “proof of closure“ switch.
Also, the timer must be approved for combustion
system use.

59. Fuel System Interlocks
– Fuel pressure switches check
that the fuel pressure is within
safe limits. Most systems have
both high and low pressure
switches.
– Above 400,000 BTUH, one
valve must be equipped with a
proof of closure switch. This
verifies that the fuel valve is
closed during purging.

60. Temperature Controllers
– Almost every oven used in industry is designed to maintain an enclosure or a
product at a specific elevated temperature. For example, an automotive
electrocoat oven might operate at 350°F. Temperature Controllers are used to
vary the heating system’s energy output to hold the oven temperature at a
specific value. In many newer and larger installations, programmable logic
controllers (PLC’s) or industrial computers are used to control the
temperature. Any of these approaches use a temperature sensor such as a
thermocouple or RTD to sense the temperature. NFPA 86 does not give
requirements for temperature controllers or even require one. Some
ovens, especially radiant heating ovens, do not have temperature controllers.

61. Excess Temperature Limit Controllers
– Every class A oven, and most other ovens, are required to
have an excess temperature limit controller that is separate
from any process temperature controller. The “high temp
limit” cuts off the energy input to the oven if the oven
temperature gets too high. The limit controller must be
listed for its service.

62. Flame Supervision
– Ovens that include fuel fired burners
must control the burner with a flame
supervision relay and appropriate flame
sensor. The flame relay is an electronic
device that has onboard logic specific to
safely controlling burners. Many flame
relays also have logic for starting
combustion air blowers or purging the
oven. Flame relays use flame sensors to
indicate the presence of a flame. Flame
rods and UV scanners are the most
popular types. A flame rod uses the
electrical conductivity of a flame to sense
the flame. A UV scanner is a device that
senses the ultraviolet radiation emitted
by the flame to sense its presence. There
are also other types of flame detectors
such as lead sulfide detectors.

63. Flame Supervision
Flame Rods are simple and reliable flame
sensors. However, the metal part of the
rod must contact the flame and therefore
it erodes over time. Generally, flame rods
are used on lower temperature processes
where access to the flame is possible.
UV Scanners require only a line of
sight to the flame, not actual
contact. They can fail in a flame
simulating manner which could
cause an explosion. On ovens
that run continuously, self checking
scanners are required. These
units continuously check for flame
simulating failure.
Flame Rod
UV Scanner
Self-Checking
UV Scanner

64. Other Interlocks
– Conveyor Interlock: According to NFPA 86, “Conveyors or
sources of flammable or combustible material shall be interlocked to
shut down on excess temperature or if either the exhaust or
recirculation system fails.”
– Fire Protection: Some oven systems are interlocked to the fire
protection system so that the oven reacts safely to a fire. An
example might be to cut off the burner if a sprinkler flow
switch actuates.

65. Operational Requirements
– Operating an industrial oven or furnace is a
serious matter and requires specific actions to
insure it is done safely. Manufacturers are
required to instruct the owner in safe operating
and maintenance procedures. Only by using the
oven within its design parameters can safe
operation be assured. To be sure the oven is
operated within safe limits, NFPA 86 requires
each Class A oven have a “Safety Design Data
Form” which must specify the following:
• Solvent used
• Number of gallons (liters) per batch or per
hour of solvent and volatiles entering the oven
• Required purge time
• Oven operating temperature
• Exhaust blower rating for the number of
gallons (liters) of solvent per hour or batch at
the maximum operating temperature

66. Operational Requirements
– NFPA 86 requires that oven manufacturers
provide instruction in safe operating procedures
including providing “clear inspection, testing, and
maintenance instructions.” In fact, NFPA 86
includes several suggested oven maintenance
checklists. These lists include, among many
requirements :
• Verification that safety devices such as pressure
switches and high temperature limits actually work.
• Checking fuel gas valves for leaks. A specific leak
checking procedure is outlined.
• Cleaning debris from ovens and ducts.