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COMBUSTION SAFETYBASICS

Joe Konopacki

Why Combustion Safety?• Hydrocarbon fuels are hazardous

– Explosion or fire is possible

– Poor indoor air quality

• Exhaust byproducts are harmful or deadly– Safe and efficient combustion

– Proper exhaust management

• Fire hazards happen thoughtlessly– Combustibles set near fire

• Our clients want a safe & healthy home– Communicate the level of risk & required action

Combustion Safety Basics

What to look for

• Ambient (breathing zone) CO

• Gas/fuel Leaks

• Combustion Air

• CO production (on all gas appliances)

• Exhaust Spillage signs

• Dryer Safety

Combustion Safety Basics

Combustion Process & CO

• CH4 + 2O2 →

• Combustion is rarely perfect

Combustion Safety Basics

2 H2O

CO2

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CO Production

• Lack of oxygen = Incomplete combustion

• Inadequate combustion air

• High gas pressure

• Dirty, Misaligned burners

• Flame impingement

• Back drafting of combustion byproducts– Carbon Dioxide (CO2) -- Nitrogen Oxide (NO)

– Carbon Monoxide (CO) -- Sulfur Dioxide (SO2)

Combustion Safety Basics Ambient (breathing zone) CO

~3 yr Sensor Life!

CO Alarms

Ambient CO Monitoring – CO Alarm

• Young, old and ill feel

effects first

• >5ppm can affect a fetus

• Position near source

Ambient (breathing zone) CO

CO Detectors

• ~3 year typical sensor service life

• Some claim 10 year service

• ‘TEST’ is for

the battery,

not the sensor

Ambient (breathing zone) CO

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Ambient CO Monitoring – CO Detector

• From time of entry

• BPI Ambient Limit: 35 ppm

• Ventilate

• Determine source

Ambient (breathing zone) CO

Detecting Gas Leaks

• “Zero Out” Outside – or not?

• Adjust/Check Sensitivity

• Slowly move sensor around joints

• Check all accessible fuel pipe and

joints

• Don’t move appliances

• Natural gas rises↑ - Propane falls↓

Gas/fuel Leaks

Reporting Gas Leaks • Confirm with soap bubble

solution?

• Tag it & Photo

• Leave a notice for homeowner

• Call out Pre-1973 Brass gas lines

Gas/fuel Leaks

Gas Leaks

• Most common issue

• Typical – 1 leak per house average

• Not ‘Normal’

• Symptoms

– Respiratory allergic reactions

– “Mold allergies”

– Respiratory sensitivity

Gas/fuel Leaks

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Combustion Air from Inside

Combustion Air

Total BTU to Volume of space

100,000 ��� �� × 50� �

1000 ���/��= 5,000 � ��

625 ft2 x 8’ tall space

Combustion Air from Outside

Combustion Air

1 ��. �� �� �������

2� ���/��

1 ��. �� �� �������

1.5� ���/��

Gas Oven Testing

Gas Oven CO Measurement

• Open window and/or turn On exhaust fan

• Test CO level in flue (undiluted stream)

• Set oven at highest setting (Broil)

• Monitor ambient CO during test (~2 ft away)

CO Production

Gas Oven TestingCO Production

Steady State

Over 100 ppm is excessive

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Gas Oven TestingCO Production

Gas Oven CO Measurement• Record CO level at 10 minutes (Steady State)

• Report CO profile

• Recommend clean, tune & re-test

• Use exhausting range hood

• Typical high CO source in homes

Gas Oven TestingCO Production

Types of Exhaust

Atmospherically vented

• Natural Draft

• Uses metal exhaust pipe

• Inside air for combustion

• Hot exhaust rises due to greater buoyancy

• Open draft hood for dilution air

• Spillage possible here

Combustion Safety Basics

Types of Exhaust

Induced Draft or

Mechanically Assisted

Combustion Safety Basics

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Types of Exhaust

Atmospherically vented

• Induced Draft or Mechanically Assisted

• Uses metal exhaust pipe

• Inside air for combustion

• Fan pulls combustion air through heat exchanger

• Fan does not push exhaust up and out

Combustion Safety Basics

• Under or through draft hood

• Access undiluted flue gases

Combustion Safety Basics

Measure CO

Types of Exhaust

• Power Vented = 1 PVC pipe

• Inside air for combustion

• Cool exhaust pushed out

• Direct Vent = 2 PVC pipes

• (a.k.a. Sealed Combustion)

• Outside air for combustion

• Cool exhaust pushed out

• Check CO outside

Combustion Safety Basics

Types of Exhaust

Power Vented = 1 PVC pipe

Direct Vent = 2 PVC pipes

Combustion Safety Basics

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Types of Exhaust

Combustion Safety Basics

• ¼” rise per foot min. for horizontal

• Min Vertical Rise (typically 3x vent diameter)

• With commonly vented units:

– Smaller Btu unit vented Above Larger Btu unit

– A Y-fitting assists natural upward draft

– Smaller unit Y’s into Larger unit

Proper Venting

Combustion Safety Basics

Improper Venting

• Blocked, or partially blocked, chimneys, vents

or vent connectors

• No chimney liner for orphaned water heaters

• Improperly designed vent system

– An indirect route

– Negative slope

– T-fittings

• Lack of code compliance

Combustion Safety Basics Combustion Safety Basics

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Combustion Safety Basics Combustion Safety Basics

Combustion Safety Basics

Improper VentingCombustion Safety Basics

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Stack Effect

House PressuresCombustion Safety Basics

•Creates negative pressure low in home

•Driven by temperature difference to outside

•Greater Stack pressure requires greater Draft pressure

Wind Effect

House PressuresCombustion Safety Basics

•Positive pressure on Windward side induces spillage

•Negative pressure on Leeward side induces draft

Make note of:•Wind direction & speed•Location of Flue

Mechanical Fans

House PressuresCombustion Safety Basics

•Bath & kitchen fans (30-1200 cfm)

•Clothes Dryer (100-150 cfm)

•Wood/gas burning stoves & fireplaces (300+ cfm)

•Whole-house fan (1000-5000 cfm)

This is whatleaky ductwork

can doto your house

Combustion Safety Basics

Supply Leaks

Return Leaks Room Imbalances

No Leaks

Consider:

•Air Handler

•Duct Leaks

•Supply/Return Distribution

•Door Closures

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House Pressures

Combustion Safety Basics

House Pressures

Combustion Safety Basics

Depressurization Limit

Limit is:

• Low for weak draft appliances

• High for stronger appliances

• Tug-of-War handicap

Exhaust Spillage Signs

Negative

CAZ Pressure

Negative

Draft Pressure

Occasional Exhaust Spillage

Exhaust Spillage Signs

•Large exhaust fans

•Wind on chimney

•Room pressures

•Flue obstruction

•Flue geometry

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ConsistentExhaust Spillage

Exhaust Spillage Signs

• Clogged flue

• FAU pressures

• Open returns

• Duct leaks

• Constant exhaust fans

• Tight home

Worst Case Pressure Testing

The goal is

to make the appliance fail.

If it can be done on purpose,

the homeowner may do it by accident.

So how much negative pressure

is too much?

Exhaust Spillage Signs

Typical

Worst Case Depressurization

Exhaust Spillage Signs

Pressure Limit = -5

CDL Exceeded-FAIL-

• Fire appliance & check for spillage for 1 minute

Spillage TestExhaust Spillage Signs

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Dryer Safety

Dryer Safety

• Vinyl or metalized Mylar will burn

• Fire hazard with gas dryers

• Recommend:

• Install metal – flex or solid

• Clean entire line of lint

• No CO testing

Issues to Look For

Combustion Safety Basics

Dryer exhaust duct material

Gas leaks

Oven CO/ Range hood venting

Combustion air requirements

Melted grommets on water heater

Corrosion near draft hood

Evidence of flame roll out

Benefits of CO Test

Combustion Safety Basics

• Detect…

• Dangerous CO

• Malfunctioning unit

• Inefficient unit

• Cracked heat exchanger - $$

• Recommend further analysis & repair

Benefits of Combustion Safety Basics

Combustion Safety Basics

•Better understanding of house pressures on combustion exhaust flow

•Safety issues to look out for•Dryer vent material•Gas leaks•Oven CO

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QUESTIONS?

Combustion Safety Basics