Risk Management
Most owners decide to implement air structures, domes or "bubbles" because they are low cost alternative to other building types. However, if they are not properly installed and maintained, the savings can be literally blown away.
Common risk management items
A good risk management program includes periodic inspections and maintenance.
Fabric Membrane
Pressurization
Typically synthetic polyester or fiberglass, coated with PVC or Teflon formulation, for resistance to ultraviolet light and to improve fire resistance. Depending on the design, the fabric can have an embedded network of steel or fabric cables for additional anchoring strength.
A combination of high output fans and HVAC equipment to maintain pressure and interior temperature. Backup is required in the event of a single fan failure. Additionally, an emergency generator should be installed for use during a power failure.
Egress
Lighting
Airlock type doors to provide entrance and exit paths. National Fire Protection Association (NFPA) Life Safety Code 101 requirements apply to the number and size of doors.
Bubbles have fairly good light transmission to the interior during daylight. Lighting can be added and can be either fixed at the interior sides or suspended from the membrane.
Maintenance
Proper maintenance and attention to snow loading are key factors in preventing an air supported structure collapse. Specific actions to prevent collapse vary by structure type and manufacturer. Refer to manufacturer's maintenance requirements and procedures to prevent snow load induced failure. Blizzard conditions, or wet snow combined with little or no wind, can cause significant snow loading in a short period of time.
Snow Removal
Fabric Life Span
Manufacturer's snow removal recommendations should be followed. Guidelines will likely include the following:
- Increase internal air pressure and/or temperature, according to the dome manufacturer's procedures, to cause the snow to break up and slide off.
- Remove snow build up from the sides of the structure to eliminate side pressure. Blizzards compound this by creating drifts on the windward side of the structure. During snow removal give specific attention to areas where the fabric joins fixed, standing objects such as HVAC systems and exit doors.
- Develop winter storm contingency plans, monitor weather forecasts and have staff available, when needed.
- Lower interior equipment and lights during heavy snow storms.
- Keep the back up generator on a maintenance test schedule.
NFPA 102 requires an annual inspection of the structure plus any required maintenance. A biennial inspection of the structure by a professional engineer, registered architect or an individual certificated by the manufacturer is also required by NFPA.
Fabric life span varies with weather, sun exposure, quality and maintenance with fifteen (15) to twenty (20) years being typical.
Other Requirements
- Surrounding vegetation or other combustible materials within 10 feet of the structure should be cleared.
- LPG tanks, where used, should be located no less than 5 feet from the structure. Tanks or gas lines should be protected from vehicular traffic.
- Provide scheduled maintenance of the blower inflation system for proper operation.
- Follow the manufacturer's requirements during seasonal take down and installation of the structure.
- The biennial inspection may result in recommended fabric replacement depending on condition.