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 Mobile ViewENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY ACCEPTABLE MOLD LEVEL ACCURACY OF VARIOUS MOLD TEST METHODS ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD ACTIVITY of MOLD in BUILDINGS AGE of MOLD - Old is the Mold? AIR CLEANER PURIFIER TYPES AIR FILTERS for HVAC SYSTEMS AIR POLLUTANTS, COMMON INDOOR AIR TEST FOR MOLD: ACCURACY AIR TEST SAMPLING CASSETTE STUDY AIRBORNE MOLD SPORE COUNT ACCURACY AIRBORNE PARTICLE ANALYSIS METHODS ALLERGEN TESTS for BUILDINGS ALLERGENS in BUILDINGS, RECOGNIZING ALLERGY & MOLD IAQ PRODUCTS ALLERGY TESTS for PEOPLE ALLERGY TEST ACCURACY ATTORNEYS and EXPERT WITNESSES ATTIC MOLD BASEMENT MOLD BASEMENT MOLD WATER IMPACT BATHROOM MOLD BROWN HAIRY BATHROOM MOLD BIBLIOGAPHY for ENVIRONMENTAL HEALTH, MOLD, IAQ BIOLOGICAL POLLUTANTS BLACK MOLD, HARMLESS COSMETIC BLACK MOLD, TOXIC & ALLERGENIC BLEACHING MOLD, Advice about BLUE vs YELLOW COMBUSTION FLAMES BOOK MOLD, Moldy Book Cleaning BOOKSTORE - ENVIRONMENTAL CACTUS FUNGI / MOLD Cadmium in the home CAR MOLD CONTAMINATION CARBON DIOXIDE - CO2 CARBON MONOXIDE - CO Carbon Nanotube Hazards CARPET DUST IDENTIFICATION CARPET MOLD CONTAMINATION CARPET PADDING ASBESTOS, MOLD, ODORS CARPET FUNGICIDAL SPRAY CARPET STAIN DIAGNOSIS CARPET & other STAIN TESTS CARPET TEST PROCEDURE CARPETING & INDOOR AIR QUALITY CARPETING, SELECTION & INSTALLATION CAT DANDER in buildings Cell phone Radiation Hazards CHINESE DRYWALL HAZARDS CHEMICAL CONTAMINANTS in WATER CHIMNEY INSPECTION DIAGNOSIS REPAIR CHLORINE IN DRINKING WATER CHLORINE in WATER, HOW TO TEST FOR CHLORINE IN SEPTIC WASTEWATER COALSTOVE SAFETY COMBUSTION GASES & PARTICLE HAZARDS COMBUSTION PRODUCTS & IAQ CONDENSATION or SWEATING PIPES, TANKS CPSC Indoor Air Pollution Book Online Copy DIRECTORY of MOLD / ENVIRONMENTAL EXPERTS DIRT FLOOR MOLD CONTAMINATION Disinfectants Disinfecting Buildings with Bleach DRYWALL MOLD DRAFT HOODS - gas fired DRAFT MEASUREMENT, CHIMNEYS & FLUES DRAFT REGULATORS, DAMPERS, BOOSTERS DRINKING WATER Diethylstilbestrol - DES DUCT SYSTEM & DUCT DEFECTS DUST ANALYSIS for FIBERGLASS DUST CONTAMINATION FROM HVAC? DUST SAMPLING PROCEDURE EMERGENCY RESPONSE, IAQ, GAS, MOLD EMF MEASUREMENT PROCEDURES ENERGY SAVINGS in BUILDINGS ENVIRO-SCARE - PUBLIC FEAR CYCLES EXTERIORS of BUILDINGS FEAR of MOLD - MYCOPHOBIA Fiberboard Insulation Sheathing Mold Fiberglass Enviro-Scare FIBERGLASS HAZARDS FIBERGLASS INSULATION FIBERGLASS INSULATION MOLD FIBERGLASS PARTICLE CONTAMINATION TEST FIBERGLASS INSULATION MOLD FIBERGLASS PARTICLE CONTAMINATION TEST FIRE DAMAGE vs MOLD DAMAGE Fireplace Inserts Fireplaces & Woodstove Contaminants FLAME COLOR, BLUE vs YELLOW COMBUSTION FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP FLOODS IN BUILDINGS-mold FLOOR DAMAGE DIAGNOSIS FLOOR & SUBFLOOR MOLD, HIDDEN FLOOR TILE ASBESTOS IDENTIFICATION FLOOR TILE HISTORY & INGREDIENTS FORMALDEHYDE HAZARDS FORMALDEHYDE HAZARDS FUNGICIDAL SPRAY & SEALANT USE GUIDE MOLD INFORMATION CENTER ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD CLEARANCE INSPECTIONS - MOLD CLEANUP CONDENSATION or SWEATING PIPES, TANKS COOLING LOAD REDUCTION by ROOF VENTS DEHUMIDIFICATION PROBLEMS DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE DUST ANALYSIS for FIBERGLASS DUST SAMPLING PROCEDURE EFFLORESCENCE, Salts & White / Brown Deposits EMERGENCY RESPONSE, IAQ, GAS, MOLD FEAR of MOLD - MYCOPHOBIA Fiberboard Insulation Sheathing Mold FIBERGLASS INSULATION MOLD FIND MOLD, ESSENTIAL STEPS FIND MOLD in buildings, HOW TO HUMIDITY LEVEL TARGET Humidity Encourages Mold Dust Mites & Bacteria What humidity level? Humidity in Basements Humidity in Attics Target Humidity Reaching the Target Measuring Humidity Tools for Measuring Humidity INDOOR AIR QUALITY & HOUSE TIGHTNESS INDOOR AIR QUALITY IMPROVEMENT GUIDE INDOOR AIR QUALITY METHODS COMPARED LEAD POISONING HAZARDS GUIDE LEED GREEN BUILDING CERTIFICATION LEED Building Designation & IAQ MEDIA BLASTING for MOLD REMOVAL METHANE GAS SOURCES MICROSCOPE DIGITAL PHOTOGRAPHY MILDEW in BUILDINGS ? MILDEW ERRORS - MOLD PHOTOS MILDEW REMOVAL & PREVENTION MOISTURE CONTROL in BUILDINGS MOLD: A COMPLETE GUIDE TO MOLD MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD MOLD ACTIVITY in buildings MOLD AGE - Old is the Mold? MOLD APPEARANCE - WHAT MOLD LOOKS LIKE MOLD APPEARANCE - STUFF THAT IS NOT MOLD MOLD ATLAS & PARTICLES INDEX MOLD CLEANERS - WHAT TO USE MOLD CLEANUP COMPANIES MOLD CLEANUP, DO IT YOURSELF MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD MOLD CLEANUP by MEDIA BLASTING MOLD CLEARANCE INSPECTIONS MOLD CLINICAL REFERENCE TEXTS MOLD CONSULTANTS/INSPECTORS MOLD CONTAMINATION LEVELS MOLD CULTURE PHOTOS MOLD CULTURE TEST KIT VALIDITY MOLD DETECTION & INSPECTION GUIDE MOLD or INDOOR AIR EMERGENCY RESPONSE MOLD EXPERT, WHEN TO HIRE MOLD GROWTH on SURFACES MOLD INSPECTORS & MOLD TESTERS MOLD PREVENTION GUIDE MOLD RELATED ILLNESS GUIDE MOLD RELATED ILLNESS SYMPTOMS MOLD TEST KITS Nanomaterials Hazards NOISE / SOUND DIAGNOSIS & CURE ODORS, Smells, Gases in buildings-Diagnosis & Cure More Information |
This article describes tools and instruments used to measure indoor humidity, relative humidity, and temperature - also giving the dew point. We discuss choices and accuracy of equipment used to measure indoor humidity level as a step in avoiding indoor condensation trouble, mold and other indoor pathogen growth in buildings. InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.It answers the question "How do I maintain to avoid mold and indoor air quality issues?" We also discuss where and how to measure indoor humidity, what indoor humidity targets to set, and we explain relative humidity, dew point, and moisture condensation in and on building materials. Readers should see DEHUMIDIFICATION PROBLEMS and MOISTURE PROBLEMS: CAUSE & CURE and also DEW POINT TABLE - CONDENSATION POINT GUIDE for an explanation of dew points and indoor humidity in buildings. HUMIDITY LEVEL TARGET explains the proper indoor humidity levels we should be trying to achieve. If you need to measure indoor humidity levels, see Tools for Measuring Humidity. If high indoor humidity is causing mold contamination, also see HUMIDITY CONTROL TO PREVENT MOLD. Also see WATER ENTRY in buildings where we describe the cause and prevention of water leakage into buildings. ROT, TIMBER FRAME describes severe damage due to indoor moisture, insulation, and vapor barrier defects. INDOOR AIR QUALITY IMPROVEMENT GUIDE includes details about whole house ventilation systems. © Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Choices of Instruments to Measure Temperature and Relative Humidity Indoors - HygrometersWhen you buy an instrument to measure indoor humidity, you must either buy one which reads the result in relative humidity or you'll have to do some calculations to factor in temperature. The old, amusing, but very accurate sling psychrometer made an "end run" around the calculation problem by swinging a wet bulb thermometer through the air, literally slinging it around in a circle at the end of a string. This motion caused the water on the bulb to evaporate. The instrument then measured the temperature drop from evaporation and enabled reading of the relative humidity.
We have found that the less costly instruments, perhaps in the $40. to $100 range, are not precise "lab-grade" instruments, but they'll generally be within 1-3 percentage points of one another - accurate enough for our purposes, particularly if the instrument is consistent in its behavior. Since these instruments have to know the temperature as well as the humidity in order to calculate the relative humidity of the air, they'll usually give the temperature reading as a bonus along with the RH reading. At left we show a low cost Radio Shack™ indoor-outdoor temperature and humidity monitor. Variations in Indoor Relative Humidity by Building Area and Surface TypeThe relative humidity, or "RH" will vary significantly in a building at a given moment, depending on where you make your observations. Here are some example RH measurements from a recent investigation at a 1970's wood frame two story home in generally good condition, after an extensive mold remediation and dryout project, where the owner had been running two dehumidifiers in the basement, and where there were no building leaks:
Notice, with no surprise, that the RH is higher close to the (cool) masonry surface? This explains our reasoning in suggesting a fairly low basement RH target for buildings if we're going to measure the RH in the center of the room. Some dehumidifiers have an RH meter built right into the machine, so it will tell you what RH level it's seeing in its incoming air. But for operating efficiency you'll often run the machine in the center of the room. The target humidity for a building, if measured at room center, needs to be low enough to avoid condensation out on cool surfaces at the room perimeter or floor. MEASURING Indoor HUMIDITY - How do you measure indoor humidity and relative indoor humidity?Relative Humidity vs. Absolute Humidity in buildingsA variety of instruments can measure the amount of moisture in air, which we call "humidity." For example an inexpensive indoor "weather station" often includes a "humidity" gauge along with a barometer and thermometer. But just knowing the level of moisture in air (absolute humidity) is not enough. Usually, the humidity targets we use in these articles, and in academic or scientific texts are numbers expressed as relative humidity which takes into account not only the absolute water level in the air, but also the air temperature. Relative humidity, by taking into account both the absolute humidity in the air and the temperature of the air, is telling you the humidity level as a function of the maximum amount of water that the air is capable of containing at a given temperature. If we're trying to control mold and other indoor pathogens for which water is a gating factor, it's relative humidity that is important. Why? Because water condenses out of air onto a building surface (and thus supports mold or other indoor pathogens) only when the air at that surface contains more water than it can hold at that temperature. When warm, moist air contacts a cool surface, your basement drywall near the floor, for example, the air touching that surface may cool and give up some of its moisture to condense on the surface. See HUMIDITY LEVEL TARGET and also DEW POINT CALCULATION for WALLS and DEW POINT TABLE - CONDENSATION POINT GUIDE for details about indoor humidity, relative humidity, and the dew point in buildings. Watch out: We recommend use of dehumidifiers and humidity instruments or humidity transmitters to monitor your building. But no dehumidification system will be up to the task of preventing mold if a building has serious leaks, flooding, or water entry. No dehumidifier, no "air cleaner," no "ozone generator," nor other magic machine, spray, or air treatment will correct a mold problem in a building if there is a significant problem reservoir. For that case, what's needed is to find the mold problem, remove it, and correct its cause. And as a last warning, there are about 1.5 million mold species - some of them may be able to grow in very dry or very wet or other inhospitable conditions. Questions & Answers regarding this article. Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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