This study guide is provided to you to complement the lecture and hands-on learning environment of
the WRT and ASD courses. Please use this guide to become familiar prior to class with
terms, formulas and basic information. When combining this pre-course study guide with
classroom instruction and homework assignments, your exam should be easier with higher
Category of Water: (source of the water)
• Category 1 (a.k.a. “clean”) - originates from a sanitary water source
• Category 2 (a.k.a. “gray”) – contaminated; may cause discomfort or sickness
• Category 3 (a.k.a. “black”) – grossly contaminated; includes toxins, pathogens
• Special Situations – regulated or hazardous materials

Class of Water: (quantity; anticipated evaporation rate; initial dehumidifier calculations)
• Class 1 – least amount of water, absorption and evaporation
• Class 2 - large amount of water, absorption and evaporation (carpet; cushion; base of walls)
• Class 3 – greatest amount of water, absorption and evaporation (ceiling; walls; insulation;
• Class 4 – specialty drying – (hardwood; plaster; concrete) – deep pockets of saturation
Principles of Drying: Remove excess / evaporation / dehumidification (ventilation) / temperature
Extraction tools:
• Light wand – perimeter of water loss; extract glue-down carpets
• Stationary tool (e.g., Water claw) – subsurface tool; extract carpet and cushion
• Self-propelled tools (e.g., Rover; Xtreme Xtractor) – riding tool; multi-speed; extract carpet
and cushion
• Vacuum squeegee – concrete; hardwood; vinyl; laminate
Evaporation tools:
• Airmovers – centrifugal (laminar); axial (high-amperage; low amperage; focus ability)
o placement – 1 for every 10-16 linear ft. of wall area; 15-45 degree focus; almost touching wall
o safety screens – intake and output areas; clean with compressed air; do not block intake
o electrical safety – lightweight extension cords; three-prong plugs; maintain electrical cord
• Structural Cavity Drying Systems (SCDS)
o vented (e.g., Turbovents 18”-48” widths; Octi-dry; Omni-dry; Air Wolf)
o injected (e.g., Injectidry; Dri-Force; Direct-it In)
• Floor Drying Systems
o vented (e.g., Air Wolf)
o injected – negative air mats (e.g., Dri-Force; Injectidry)
• Air Filtration Devices – AFDs (negative air machines - NAM; air scrubbers; HEPA filters)

Dehumidification equipment: AHAM rating – pints removed at 80º F / 60% RH in 24 hours
Type Reduced Performance
Type Dehumidifier Temperature Relative Humidity Specific Humidity (gpp)
Standard refrigerant 68º F. / 20º C 60%
Conventional 33º F. / 1º C 40%
Low Grain Refrigerant (LGR) 40º F. / 4º C 30% 28-35
Desiccant (with silica gel) 32º F. / 0º C – below 10% - below 10-15 -

Refrigerants – Most efficient operating conditions 70º - 90º F. (most energy efficient)
• Desiccants – most efficient with incoming air from coolest/driest air possible; capable of
creating pressure differentials; produces low specific humidity required to dry Class 4 materials
• Uses - closed-drying environments; multiple layers of materials; security limitations; high
outside (and inside) humidity conditions; no ventilation ports; basement areas
Initial dehumidification calculations (psychrometric readings dictate further requirements after
first day)

Type: Class 1 Class 2 Class 3 Class 4
Conventional 100 40 30 N/A
LGR 100 50 40 50
Desiccant 1 ACH 2 ACH 3 ACH 2 ACH

Electrical / Heat / Energy:
• Amperes (amperage or “amps”) – the amount of electricity (current) flowing in a circuit
• Voltage – the force of electricity flow in a circuit
• Watts – the amount of electricity an electrical device uses when operating
• British Thermal Units (BTUs) – heat generated by electrical device
o Formula – amps x volts x 3.4 = British Thermal Units (Btu) per hour
o HVAC – unit removes 12,000 Btu per ton
• Residential v. commercial - generally, residential 15 amp / commercial 20 amp
• 220 splitters – use where there is limited amperage or fuses
• Use no more than two, five-amp airmovers per 100 ft., 12 gauge extension cord
• Power consumption formula – volts x amps x 24 hours = watts ÷ 1000 = kw x cost per kw per day
Inspection equipment:
• Moisture sensor – senses moisture in materials over 17% MC; helps determine perimeter of
water damage; unable to determine which layer is wet or when dry
• Thermo-hygrometer – determines temperature / RH in all required atmospheric areas of
inspection; helps determine open or closed drying system; further determines dehumidifier
requirements after initial placement

• Moisture meters – invasive and non-invasive; determines moisture content; establish, monitor
and determine when dry standards are met

• Miscellaneous – infrared camera and thermometer; manometer; borescopes; data loggers

Chemicals / biocides (antimicrobials)
• Sterilizer; disinfectant; sanitizer
• Provide written informed consent to customer; advise occupants to leave during application;
• Government-registered disinfectants – document application details; apply only per label
• EPA – Environmental Protection Agency (U.S. federal agency with regulatory control over
• F.I.F.R.A. – Federal Insecticide, Fungicide and Rodenticide Act – U.S. federal regulations
administered by EPA

Floorcovering carpet:
• installation methods – stretch-in, direct glue-down, double glue-down
• drying methods – in-place, full float, partial float
• construction – woven – Axminster, Wilton; usually natural fibers; tufted – primarily synthetic
• delamination – separation of primary - secondary backings; laminate strength loss up to 85%
when wet
• Category 3 – must remove and dispose; IEP may be required for testing

Floorcovering cushion (also known as padding, underlay):
• types – foam (prime, bonded urethane); rubber; felt (hair/jute, synthetic); porous and
• Category 2 and 3 - must remove and dispose; if Category 2 – hot water extraction of carpet

Floorcovering wood (strip wood, plank wood, engineered – laminated wood, parquet)
• non-destructive (non-rotting) fungal growth - over 16% MC
• destructive (dry rot) fungal growth – over 20% MC
• fiber saturation (wet rot) – 28 – 30% MC
• damages from moisture - (cupping; crowning; buckling; heaving)
• dry within 2-4 percentage points of EMC drying goal

Floorcovering (laminate; resilient, tile)
• limitations (trapped water, potential asbestos, ceramic tile – sealed grout; trapped water)
• layers of floorcovering; dry flooring as a system

Microbiology (fungus; bacteria; virus)
• conditions for growth
o organic food source (cellulose)
o moisture (or high humidity)
o temperature (most prolific 68-86º F. / 20-30º C.)
o stagnant air
o time (some 1-2 days; others up to 10-12 days in chronic conditions)
• ANSI/IICRC S520 – Standard and Reference Guide for Professional Mold Remediation
• Indoor Environmental Professional (IEP) – specialized experts may be required
• Mycotoxin – a potentially harmful metabolite produced by some fungi, especially molds.
• Endotoxin – a portion of the outer cell wall of some gram-negative bacteria. When ingested or
respired, endotoxins can cause fever, changes in white blood cell counts, increased airway
resistance, shock and even death.

Psychrometry definitions:
• Psychrometry – study of the relationship between air, humidity and temperature and their
effect on various materials and comfort levels
• Psychrometric chart – chart consisting of lines and curves that shows the relationship between
air volume, temperature and relative humidity, and from which a variety of other information
(specific humidity, dew point, vapor pressure, etc.) relating to drying may be determined
• Dew point – the temperature at which humidity in air reaches saturation (100% RH) and will
condense from that air to form condensation or “dew” on surfaces.
• Evaporation – the process of changing a liquid to a vapor
• Primary damage – damage sustained as a result of direct exposure with water.
• Secondary damage – damage sustained from indirect or prolonged exposure to disaster
• Relative Humidity (RH) – the amount of moisture in a given volume of air, expressed as a
percentage of the total moisture holding capacity of that volume of air, at a given temperature.
As temperature increases, humidity „relative‟ to the total air volume decreases; conversely, as
temperature decreases, RH increases.
• Humidity ratio (specific humidity) – the weight of suspended moisture in air expressed in
grains per pound (gpp) of dry air (14 cubic feet of dry air equals one pound). 7000 grains of
water vapor equals one pound of water. As specific humidity (humidity ratio) changes, there is a
corresponding change in vapor pressure on the surrounding environment.
• Grains of moisture per pound (gpp) – unit to measure specific humidity (humidity ratio), or
the weight of moisture in air, expressed in grains per pound (gpp) of dry air.
• Balanced drying – ideal drying situation in which the rate of evaporation is equal to or
slightly less than the rate of dehumidification or ventilation.
• Dehumidification / ventilation – reducing (exchanging) moisture content of air
• Dry bulb temperature – temperature registered by a thermometer
• Hygroscopic – material that readily absorbs and retains moisture or water vapor from air in an
attempt to reach equilibrium.
• Moisture content (MC) – weight or percentage of moisture in materials, as compared to the
weight of oven-dried, like material. (Wood with 10% MC indicates that 100 pounds of that wood
contains 10 pounds of water and 90 pounds of wood).
• Permeance – a measure of water flow through material(s) of specific thickness.
• Sublimation – phase-transition in which a solid is transformed into a gas while bypassing the
intermediate liquid phase (e.g., dry ice; freeze drying).
• Vapor pressure – pressure on surfaces exerted by substances in a gaseous state; directly
related to (reduced through) dehumidification.
• Vapor barrier – material through which moisture can‟t readily pass (permeance factor of 1 or
• Saturation – point at which air or materials can absorb no more moisture; point at which
drying stops; point at which air temperature has reached dew point (100% RH).
• Grain depression – reduction of specific humidity (grains; gpp) as noted in difference from
ambient air to output on dehumidifier, and as well noted in other area differentials (e.g., inside
air – outside air; affected air – unaffected air; ambient air – HVAC register output) showing
moisture removal

Balanced drying characteristics:
• Humidity, airflow and temperature “HAT” work together and when managed, enable achieving
target time for drying
• “HAT” all influence movement toward equilibrium – wet seeks dry; hot seeks cold; high vapor
pressure seeks low vapor pressure
• Vapor pressure is directly related to humidity ratio (specific humidity) and dew point

• As heat is applied to a material, energy is added; raising the temperature of a wet material
increases the rate of evaporation, further releasing moisture from the material, changing the
internal vapor pressure
• The greater the difference between ambient temperature and dew point temperature, the greater
the potential for faster and more efficient drying.
• Open drying – intentionally exchanging indoor with outdoor air without using dehumidifiers
o requires constant monitoring; above 80ºF/ 27ºC – microbial growth highly probable
o requires rapid exhausting of wet air; concerns of reaching dew point temperature
• Closed drying – use of mechanical dehumidification
• Heat drying systems – creates lower RH; requires rapid and massive ventilation of wet air to
the exterior; increases rate of evaporation by increasing the surface temperature of wet materials

Common items to all drying jobs:
• Proper authorization (contract, payment terms, responsible parties)
• Protect contents from further damages; identify primary, secondary, and pre-existing damages
• Activation of site assets (ceiling fans, whole-house fans, exhaust vents, HVAC, open drying)
• Initiate extraction procedures (contain migrating water; remove excess moisture)
• Set up evaporation and dehumidification (ventilation) equipment to promote drying
• Customer communication; determine drying goals
• Project monitoring (frequency, activities, forms, documentation)
• Completion procedures (e.g., clean flooring; demolition; reconstruction, as required)

Other Common Industry Acronyms:
• AHAM – Association of Home Appliance Manufacturers
• ANSI – American National Standards Institute
• CRI – Carpet and Rug Institute
• NADCA – National Air Duct Cleaners Association
• OSHA – Occupational Safety and Health Administration
• PLRB – Property Loss Research Bureau
• SCRT (ISCT) – Society of Cleaning and Restoration Technicians
• WLI – Water Loss Institute
• ASHRAE – American Society of Heating, Refrigeration and Air Conditioning Engineers
• ACH – air changes per hour
• ACM – asbestos containing material
• BBP – bloodborne pathogen
• gpp – grains per pound (g/kg) – grains per kilogram
• HEPA filter – High Efficiency Particle Air filter
• IH – industrial hygienist
• LKQ – Like Kind and Quality
• MVOC – microbial volatile organic compound
• EMC – equilibrium moisture content
• ERH – equilibrium relative humidity
• MSDS – material safety data sheet
• aw – water activity