What are hydrocarbon combustion fuels?
Fuels like natural gas, propane, oil, and wood, that are composed of hydrogen and carbon. During combustion, oxygen combines with hydrocarbons, splitting the molecules and releasing heat.
What are the byproducts of combustion?
Carbon dioxide, water vapor, carbon monoxide (byproduct of incomplete combustion), oxygen, heat, and NO2, SO2, VOCs
What is spillage?
The release of combustion of by-products from combustion appliances during operation.
What is backdrafting?
Continuous spillage at a flue
What causes carbon monoxide release?
Describe carbon monoxide.
Colorless, odorless, undetectable by senses - CO blocks oxygen to the brain and vital organs
What are the most effective solutions to handle dust?
Source control - don’t generate dust, cleaning, effective HVAC filters
What are some common VOC sources?
Combustion, solvents and cleaners, paints, furniture, drapery and carpet, gasoline
Where does radon come from?
What is Asbestos?
A known carcinogen if inhaled. Comes from pipe insulation, floor tile, siding and roofing
What’s the number one enemy of buildings?
What is capillary seepage?
Liquid water moving through tiny spaces. It redistributes water from liquid sources.
Water vapor moves in what two ways?
Through air movement and vapor diffusion. Diffusion movement depends on the permeance of the object and the vapor pressure difference.
What are some sources of liquid water in buildings?
Roof leaks, malfunctioning gutters, poor site drainage, undetected plumbing leaks
When do ice dams occur?
When snow melts and refreezes at a cold eave forcing water under the roofing and into building. They are a heat leakage problem, not roof.
Water vapor always flows from…
high pressure to low pressure (wet to dry)
_________ drives vapor diffusion through a difference in absolute humidity on two sides.
T/F: Water vapor is smaller and lighter than air.
What is relative humidity?
The percentage of the max moisture that air at a given temperature can hold. At 100% TH, air is saturated with moisture and condensation will occur with any additional moisture.
As air cools, its relative humidity _____.
Condensation problems increase with:
Increase in absolute humidity
Decrease in temperature
A bathroom fan should have a CFM rating that provides ___ _______.
8 ACH (Air changes per hour)
Year-round natural ventilation should only occur in the following locations:
Attics and crawl spaces
Most codes require 1 square foot of vent for every ____ square feet of attic area.
Should crawlspaces be vented?
No, they should be closed and conditioned.
How does and air conditioner work?
By passing indoor air over a cold coil, condensing water vapor and removing latent heat. ACs produce cool dry air.
How does a dehumidifier work?
Dehumidifiers pass indoor air over a cold coil but then pass the same air over the warm coil. They produce warm dry air.
What are some effective interior air barriers?
Drywall, concrete, plywood, and Tyvek
What are some effective exterior air barriers?
Concrete, plywood, some rigid insulation boards, weather resistant barriers (felts, tyvek)
What’s a vapor barrier?
A barrier that prevents water vapor from diffusing into building cavities. Exp. polyethylene sheeting, vapor-barrier paint
What are the two primary strategies for ventilation?
Ventilation through air leakage and mechanical systems
What are 3 types of mechanical whole-house ventilation?
Exhaust, supply, balanced
How does a central exhaust ventilator work?
It pulls air out of rooms and exhausts it outdoors. Make-up air infiltrates through air leaks in the building shell. The house is under negative pressure.
How does supply ventilation work?
The air handler draws filtered outdoor air into the home, pressurizing it. Stale indoor air exits through air leaks.
How does balanced mechanical ventilation work?
It supplies and exhausts ventilation air through a dedicated system. It doesn’t rely on infiltration/exfiltration. It reduces energy, safety, and moisture problems. Uses and HRV or ERV.
What does a Heat recovery ventilator (HRV) do?
Transfers heat between incoming and outgoing ventilation air streams. Recommended for cold/dry climates.
What does an Energy recovery ventilator (ERV) do?
Transfers heat and moisture between incoming and outgoing ventilation air streams. Recommended for hot/humid climates.
What are some steps in a Health and safety audit?
Identify combustion sources, verify CO detector and smoke detectors, identify dust and VOC sources, lead and asbestos, determine adequate ventilation, etc