The system consists of a set of Environmental Control Units (ECUs) designed to control temperature, humidity and provide the requested life support redundancy to the Diving Decompression Chambers.
The Drass range of products is based on the well-known technology of a pressurized high head root blower. Drass introduced this configuration in 1970s and the current ECUs are sons of this proven and reliable solution.
The equipment proposed by Drass as primary environmental control unit is supplied in three versions. The traditional reliability and efficiency of the classic ECU can now be enhanced by a high-end Siemens control logic for the i-Life version, while new stainless steel scrubbers and new interlocking mechanism systems are installed on all versions.
Assignment of the ECUs to the different locks:
Drass ECUs have heating and cooling capacity both rated more than 18 kW. This allows keeping an adequate reserve of power to ensure an excellent performance in dehumidification, heating and cooling, even when more locks are connected to the same ECU, beyond 30 m3 of total volume. The blower works with variable speed and can be regulated at the right speed for the chamber condition.
Efficiency of the blower:
Considering a 30 m3 area, a minimum recirculation rate of about 3 times per hour will be allowed at every depth level, while the rate will be significantly higher at intermediate depth (i.e. 5 recirculation per hour at 150 MSW or almost 8 times per hour at 50 MSW).
With reference to the environmental parameters, the humidity removal and odor filtering capacity will be maintained above normal standards considering the possibility of:

• Using a portion of the external scrubbers with dedicated charcoal, still keeping a high efficiency for CO2 removal.
• Using a portion or even the entire space of the internal scrubbers with dedicated charcoal and other traps. The emergency service of the internal scrubbers will always be available in emergency loading the whole scrubber with soda lime when needed.

Ancillary equipment for ECUs:
Overall cooling and heating capacity can be chosen according to customer requirement and system extension.
The standard configuration uses chillers and heaters with a dedicated set of on board pumps providing redundancy and interchangeability to the life support configuration.
All chillers are supplied with internal active redundancy: twin compressor and twin cooling circuit.
All heaters are supplied with a set of resistors which power can be reduced in case of faults and continue working in a reduced capacity mode.
All heaters are supplied with a set of resistors which power can be reduced in case of faults and continue working in a reduced capacity mode.
Stand-alone ECUs use internal heating and cooling units which do not need to install such an arrangement.
Internal Regeneration Systems:
A set of internal scrubbers and heat exchangers is provided with all chambers of a 100 Series diving system. This is available as emergency method for continuing environmental control when main power for the entire environmental control system is missing.