Study Guide - Water Damage Restoration/Applied Structural Drying (WRT/ASD)

Q: What tools and measurements are used to inspect moisture and drying conditions?

Moisture sensors detect moisture over 17% MC and help map perimeter damage but cannot identify which layer is wet or when it is fully dry. Thermo-hygrometers determine temperature and relative humidity for inspection areas and support decisions about open/closed drying systems. Moisture meters (invasive and non-invasive) measure moisture content to establish and monitor when dry standards are met.

Sep 30, 2026

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Study guide supporting WRT/ASD courses, designed to prepare learners with key terminology, formulas, and foundational concepts before lectures and hands-on practice. Covers water categories and classes by contamination level and estimated evaporation/quantity, then details drying principles and the selection of extraction, evaporation, and dehumidification equipment. Includes psychrometric and calculation guidance, AHAM-based dehumidifier context, electrical/heat/energy definitions with BTU and power formulas, inspection tools, moisture testing, and antimicrobial/blocker considerations, plus carpet installation and construction basics.

LanguageEnglish

CategoryExam

FormatPDF

Pages7

Reading Time18 min

AccessFree to download

Water Categories

Category 1, 2, 3 and Special Situations

Water Classes

Class 1-4 and specialty drying

Principles of Drying

Extraction, evaporation, and dehumidification

Drying Equipment

Extraction tools; evaporation tools; dehumidification equipment

Dehumidification and Psychrometric Calculations

AHAM rating and initial calculations

Equipment Performance Table

Types of dehumidifiers by temperature and humidity

Electrical, Heat, and Energy

Amps, volts, watts, BTUs, and power consumption formulas

Inspection Equipment

Moisture sensors, thermo-hygrometers, moisture meters, and misc tools

Chemicals and Blockers

Biocides and application documentation

Floorcovering and Carpet

Installation and drying methods; construction and delamination

Study Guide-Water Damage Restoration/Applied Structural Drying (WRT/ASD) This study guide is provided to you to complement the lecture and hands-on learning environment of the WRT/ASD courses. Please use this guide to become familiar prior to class with terms, formulasand basic information. When combining this pre-course study guide with classroom instruction and homework assignments, your exam should be easier with higher retention. Category of Water: (source of the water) • Category 1 (previously known as “clean”)– originates from a sanitary water source • Category 2 (previously known as “gray”)– contaminated; may cause discomfort or sickness • Category 3 (previously known as “black”)– grossly contaminated; includes toxins, pathogens • Special Situations – regulated or hazards materials (IEP recommended in most situations) Class of Water: (quantity; anticipated evaporation rate; initial dehumidifier calculations) • Class 1 – least amount of water, absorption and evaporation; less than 5% • Class 2 – large amount of water; absorption and evaporation (carpet; cushion; base of walls) 5%– 40% • Class 3 – greatest amount of water; absorption and evaporation (ceiling; walls; insulation; flooring) over 40% • Class 4 – specialty drying –(hardwood; plaster; concrete)– deep pockets of saturation Principles of Drying: Remove excess / evaporation / dehumidification (ventilation) temperature control Extraction tools: • Light wand – perimeter of water loss; extract glue-down carpets; follow-up extractionstationary tool • Stationary tool (e.g., Water claw; Flash Xtractor)–subsurface tool; extract carpet and cushion • Self-propelled tools (e.g., Rover, Xtreme Xtractor)-self-propelled riding tool; multi-speed; extract carpet and cushion • Vacuum squeegee-concrete; hardwood; vinyl; laminate • Submersion pumps-Formula- (ft²x inches deep) ÷ 12” = ft³water x 7.48 = water volume Evaporation tools: • Airmovers – centrifugal (laminar); axial (high-amperage; low amperage; focus ability)ο placement – 5 – 45 degree focus; almost touching wall ο safety screens – intake and output areas; clean with compressed air; do not block intake ο electrical safety – lightweight extension cords; three-prong plugs; maintain electrical cord safety • Structural Cavity Drying Systems (SCDS) ο vented (e.g., Turbovents 18” – 48” widths; Octi-dry; Air Wolf) ο injected (e.g., Injectidry; Dri-Force; Omni-dry; Direct-it In) • Floor Drying Systems ο vented (e.g., Air Wolf) ο injected – negative air mats/panels (e.g., Dri-Force; Injectidry) Dehumidification equipment: AHAM rating-pints removed at 80° F/ 60% RH in 24 hours Type Reduced Performance | Type Dehumidifier | Temperature | Relative Humidity | Humidity Ratio (gpp) | | --- | --- | --- | --- | | Standard refrigerant | 68° F. | 60% | 55-60 | | Conventional | 33° F. | 40% | 55-60 | | Low Grain Refrigerant | 40° F. | 30% | 32-35 | | Desiccant (with silica gel) | 32° F. | 10% -below | 10 – 15-below | • Refrigerants – Most efficient operating conditions 70° -90° F. (LGR, most energy efficient) • Desiccants-most efficient with incoming air from coolest/driest air possible; capable of creating differentials; produces low humidity ratio (gpp) advised 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 requirements after first day) | Type | Class 1 | Class 2 | Class 3 | Class 4 | | --- | --- | --- | --- | --- | | Conventional | 100 | 40 | 30 | N/A | | LGR | 100 | 50 | 40 | 40 | | Desiccant | 1 ACH
(÷ 60) | 2 ACH
(÷ 30) | 3 ACH
(÷ 20) | 3 ACH
(÷ 20) | 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

FAQs

How are water categories defined in WRT/ASD?

Category 1 comes from sanitary water sources, Category 2 is contaminated and may cause discomfort or sickness, and Category 3 is grossly contaminated and includes toxins and pathogens. Special situations cover regulated or hazardous materials.

What distinguishes water classes (Class 1 to Class 4)?

Classes are based on quantity, anticipated absorption/evaporation behavior, and evaporation rate. Class 1 is the least amount of water (<5%), Class 2 is 5%–40%, Class 3 is over 40%, and Class 4 is specialty drying involving deep pocket saturation materials.

What tools and measurements are used to inspect moisture and drying conditions?

Moisture sensors detect moisture over 17% MC and help map perimeter damage but cannot identify which layer is wet or when it is fully dry. Thermo-hygrometers determine temperature and relative humidity for inspection areas and support decisions about open/closed drying systems. Moisture meters (invasive and non-invasive) measure moisture content to establish and monitor when dry standards are met.

Sep 30, 2026

Upload by วิน