• -C.A.A. - the Clean Air Act dictates whether a condition exists for containment and treatment. After the need for odor and emission control has been determined, whether regulatory driven or good neighbor driven, additional laws and regulations dictate the manner of treatment.
  
  
• - NFPA 820 (National Fire Protection Associates Publication 820) Fire protection in Wastewater Treatment and Collection Facilities mandates the rate of air exchanges for various components within a wastewater facility. The law provides for the elimination of unhealthy and potentially explosive conditions due to unsafe concentrations of votatants and explosive elements.
  
  
• - O.S.H.A. 1910.146 Permit required Confined Spaces (Publication O.S.H.A. 3138) mandates work and operational requirements that are to be observed in areas and spaces that potentially are defined as confined spaces. Most enclosed areas within a wastewater processing plant fall within the confined space definition. A space that contains - or has the potential for engulfing an entrant, whether accidentally or by intent - while out of view of other plant personnel is to be viewed as a confined space.
  
  
• Too often systems are constructed with a concern for aesthetics and the desire to match existing structures -overlooking safety and concerns.

Air Volume is of major concern. Air handling fans and blowers that move air to processing units operate 24 hours a day. Every CFM and every additional Horse Power required for larger equipment increases plant operating costs.

A flat structure compared to a domed structure has different requirements for air handling. The guidelines for air exchange rates are mandated by NFPA as well as O.S.H.A. Confined Space regulations. Flat covers lower air volume and they require a lower rate of hourly air exchanges. The mandated rate is 4-6 for flat covers; 12-16 for raised domed structures.

Domes require bigger scrubbers consuming more chemicals, requiring greater disposal costs and higher maintenance costs.

Increased costs for major components are due to bigger fans and blowers, heavier and bigger ducts, and larger scrubbers. These items are required only when domes and raised structures are contemplated. Maintenance costs for the costlier, bigger equipment are also greater. When these items are added up and included in the containment system costs, the results favor a flat cover system.