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Disaster Advice Glossary
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Disaster recovery and restoration can be veiled in mystery to the many who have not undertaken specific training. This glossary explains technical terms to assist both report writing and the understanding of those technical terms so often misunderstood.
Definition
| Ambient: |
referring to the encompassing air, the indoor air of a room, wall or whole building. See Ambient Humidity. |
| Ambient humidity: |
the indoor humidity of a builfing that is within a range of comfort, typically between 35-60% humidity. Restorative Drying Note: Ambient humidity is effected by the indoor water damages. Flooded building's receive indoor humidity loads from 70% to 95% which must be removed and controlled before fungi growth occurs. Often wet building wall cavities are hidden and they are not identified as being a wet building issue, resulting in poor ventilation and increased molds. See Absolute Humidity, Fungi, Relative Humidity |
| Bounce Back: |
In restorative drying, the term bounce back refers to ambient humidity that appears to be under control when using a dehumidification process, but when that process is removed or turned-off, bounce back occurs, resulting in the return of increased ambient humidity. Restorative Drying and Education Note: For example, a wall drying system that is turned off because the face of the drywall appears to be dry, including moisture measurement of the face of the drywall. Bounce back occurs when trapped humidity or condensation results in the wall cavity, due to the drying or dehumidification process being turned off too soon or before the total wall cavity and surrounding building materials (and insulation) are allowed to completely dry. Bounce back has been studied and recurred, and it is not unusual for a wall cavity to indicate a reduced moisture content of 30%, but 12 hours later, the wall cavity reads 60% Rh. See Dehumidification Shock |
| Carpet Cushion: |
An underlayment material that is placed under a carpet. Education Note: The cushion acts like a pad, in that the cushion softens the carpet while protecting the face fibers and secondary backing of the carpet. A good carpet cushion adds life to a carpet, especially in high traffic areas. Restorative Drying Note: After a major flood, the carpet cushion should be removed to aid in the immediate drying of the building, then, if the carpet is still in place, removal of the cushion will aid in the drying of the carpet. The problem with drying a building with carpet cushion and/or carpet remains in place, are these saturated materials increase the drying time of the building, as well as they increase the ambient humidity as long as they remain wet. Litigation, Health and Safety Note: Drying carpet cushion and carpet in place may result in unwanted mold growth and increase allergens. All sewage saturated carpet cushion must be carefully removed and disposed. Leaving sewage contaminated carpet cushion in place has been known to result in sickness and illness. |
| Dehumidification Shock: |
A term used in restorative drying, to describe the process and means of dramatically decreasing the ambient humidity in a wet building environment within a relatively short period of time. Education and Restorative Drying Note: A dehumidification shock approach is warranted when the environment is severely wet and where time is on the side of mould growth, or where secondary damage is about to occur, if the trapped building water and humidity are not abated within a short period of time including a matter of hours. Large refrigerant and desiccant equipment are necessary to provide dehumidification shock. Calculating the grains of moisture in wet air, making assumptions about the amount of trapped water and moisture in building materials along with temperature and humidity readings, must carefully be calculated for a dehumidification shock equation before considering using this dehumidification process. |
| Drying Conditions: |
The ideal conditions after cleanup which allow a wet building to become ready for drying. Restorative Drying Note: In water damage remediation, it is the condition of the indoor air at any one time during the building drying process. a) The drying conditions of a wet building are influenced by the amount of standing water, water vapour in air, saturated water in wall cavities, floors and contents, condensed moisture vapour on other building materials and contents, the relative humidity and temperature outside, and the ambient humidity and temperature indoors. b) The building drying conditions must take into account the amount of water that flooded the building, its source, is the water considered contaminated, the amount of porous building materials, the amount of total moisture content in saturated building materials and contents. See Dehumidification, Thermalgraphic Chart Recording. |
| Humidity: |
The measurement of moisture and moisture-vapor in air. See Absolute Humidity, Ambient Humidity, Relative Humidity. |
| Humidity Gradient: |
The measurement of ambient indoor humidity at different layers or heights, where the ambient humidity monitoring shows an increase or decrease of humidity. |
| Performance Humidity Curve: |
A temperature and humidity graph depicting the performance of humidity from a water damage while in a buildings atmosphere. Restorative Drying Note: The performance curve of humidity as vapor pressure in a building during dehumidification, will most likely be different than the trapped humidity vapor pressure located inside wet wall cavities. Monitoring the performance humidity curve is a critical component in managing wet building drying. See Ambient Humidity, Permeability Factor, Relative Humidity, Specific Humidity, Thermalgraphic Chart Recorders/Sensors. |
| Relative Humidity: |
The ratio of the quantity of water vapour present in a room or building atmosphere, to hold and retain the water vapour, measured against the quantity of water vapour that would saturate it at any specific temperature. Restorative Drying Note: In wet-water damaged buildings, if its relative humidity is 75% in the surrounding air, the air contains 3 quarters of the total amount of water vapour which it is capable of holding, at a temperature and atmosphere pressure in the room at the time of the measurement. Change in temperature and pressure will change the relative humidity. See Absolute Humidity, Ambient Humidity, Condensation, Dew Point, Drying Conditions, Evaporation, Grains of Moisture, Psychometrics. |
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