Remote Location Microclimate Control Unit for Museum Display Cases and Storage Enclosures

Preservatech’s Maxi One constant volume humidity generator is a fully automatic positive pressure air supply device, designed to provide conservation-quality humidity control for museum display or storage enclosures. A single microclimate unit in a remote location (such as a machine room) can reliably maintain extremely stable humidity control and pollution abatement for an entire gallery of showcases.


Use these units to supply air to multiple display cases, very large volume showcases, multiple storage enclosures or small archive rooms where:

  • Energy cost savings of up to 50% are to be realized.
  • Accurate humidity control in new or renovated galleries may be expensive or impractical.
  • Existing air conditioning systems or building envelopes cannot maintain adequate humidity control.
  • Existing display cases with moderate to high leakage rates must be used, or cost savings must be found on new display or storage cases.
  • Pollutants or dust from internal or external sources must be purged from cases.



These units provide a continuous low-pressure flow of filtered air to display or storage cases, gently displacing case air and pollutants. Air is supplied as a positive pressure feed only, there is no return flow. Displaced air from the case is exhausted through naturally occurring leakage.

Display cases are fed by an air delivery system consisting of distribution pipes and small hoses. Air enters the display case through a small unobtrusive hole, requiring minimal modifications. MAXI ONE units operate independently of building HVAC systems.

The ultimate control capacity of any MAXI ONE unit will be dependent on a number of factors, including: target humidity, enclosure size, enclosure leakage, air distribution system, average ambient temperatures and the degree and speed of ambient temperature changes. Each MAXI ONE unit can supply a large number of cases of varying sizes. We can recommend a consultant to assist you in determining the most effective device for your application.

Typically, a single unit can supply a constant flow output air at an RH level from below 35% to above 60% at ambient temperatures of 70 degrees F / 21 degrees C. Lower ambient temperatures will allow the unit to maintain lower delivery RH levels Output variation at constant temperature is typically less than +/- 1%. Depending on unit and application, outputs can be from less than 15 to over 30 cfm / 500 to 1000 lpm, with a maximum treatment capacity of from 5,000 to 14,000 cubic feet / 150 to 500 cubic metres of display or storage enclosure(s).

Moisture content of the supplied air will be automatically adjusted with changes in ambient temperature to provide constant RH. (Output change is limited to a change in dewpoint of not more than 2.5 degree C per hour.) The unit will respond to changes in ambient temperature by modifying its humidity output, but will not influence or control display case temperatures. No operator adjustments to fan speed, pressure, or delivery rate are needed (or possible).

Output from the unit is constantly monitored by a sensor mounted in the gallery. Air flow outside of preset limits will be dumped by an electromechanical valve. Air is filtered for gaseous and particulate pollutants upon intake to the MAXI ONE unit, and output air is filtered through a HEPA grade filter.


The MAXI ONE unit can be located up to 400 feet / 150 meters from the gallery. The unit may be placed in a machine room, janitorial closet, or any space with adequate room for the unit, ventilation, water supply, floor drain, and power connections. The foot print of the unit is 3 ft wide X 2 feet deep (90 cm X 60 cm), and space should be allowed to access the unit for control and maintenance. Unit should be floor mounted, and comes on casters for easy movement.

The unit comes complete with a high quality temperature and humidity sensor. One sensor for each MAXI ONE unit must be located in the gallery. Sensors may be wall mounted, or placed in a “representative” showcase. Microclimate data is returned to the control panel on the unit by cable or wireless system.

The air distribution system is an integral and major component of this microclimate control system. Appropriate pipe locations, sizes, supply nodes, and placement of the safety dump valve and sensor should all be planned as early a possible in the design process. As the operating paradigms and air distribution system of MAXI ONE units are quite unique, common paradigms for installation and air ducting are usually not applicable.

The most common style of installation is “tree and branch” air supply systems using two inch lightweight copper (DWV) pipe running from the machine to the gallery, with delivery to the cases via one half inch rigid pipe or flexible hose. Bends in the system should be minimized. Other pipe sizes, materials (ABS plastic, etc.) and designs (eg “spoke and wheel” or multiple node style) or other distribution systems may be recommended, depending on installation.

We strongly suggest you engage an appropriate consultant to assist your relevant architects, engineers, and museum designers with preliminary planning of unit and air distribution systems to ensure a successful installation. Preparation of the machine location and installation of air distribution system can be done by standard trades. Our guarantee is limited to the operation and delivery capacity of the unit, not it’s interface with the enclosures nor their behaviour.

All units are supplied complete with locking casters, plugs and sockets for electrical and wiring connects, and standard compression plumbing fittings, so that units may be easily rolled into position and quickly installed.

Typical Air Distribution Diagram

This diagram represents the most common air distribution designs. Many variations are possible.

Note that bends are 45 degrees rather than 90 degrees.


  • Unit Size: 36″ wide x 24″ deep x <72″ height (including 4″ diameter swivel casters) Nominal Weight: <300 lb (reservoir empty), <500 lb (reservoir full)
  • Power Supply: As Requested, or 110V/220V/1/60, 3 wires plus ground, 30 Amp
  • Nominal Power Consumption: 12 Amps @ 220V when generating 50% RH @ 21C Maximum Operating Amperage: 23 Amps @ 220V/1/60
  • Operating Temperatures 10 – 30 degrees C; Gallery temperatures have no effect on unit mechanical operation, but will affect achievable humidity levels
  • Filter Media: Intake filter: Combination of (Carbon / PP / Fine Particulate filters); Exit filter: HEPA grade, or As Requested
  • Water Supply: 1/4″ hose connection for domestic line, or optional reservoir
  • Drainage: Floor drain in vicinity of unit, or optional containment tray
  • Output: When shipped, the MINI ONE is may be optimized to provide a constant flow of RH tempered air at tolerances as low as +/-2% within an operating range of 15 to 30 degrees centigrade at a flow of up to 30 SCFM / 1000 lpm and pressures of 3 to six inches wc at the output pipe. This air flow may be adequate to supply up to 6000 cubic feet / 200 cubic meters of display cases at four air changes per day. Ultimate device capacity will depend on the combined leakage of cases, layout of supply runs, and desired performance parameters.
  • Standard Accessories Included: Off-site alarm connections; gallery mounted sensor box; electromechanical dump valve; operating manual and trouble-shooting guide Features:
  • Provides conservation quality humidity control for very large display volumes, or multiple storage cases.
  • Accurately and consistently delivers humidity levels within 2% of set points.
  • Higher pressure output allows for effective and inexpensive air distribution systems.
  • Positive pressure ventilation with filtered and scrubbed air reduces case maintenance; pollutant and particulate inflow into cases is prevented.
  • Off-gassed pollutants generated in the cases are constantly flushed; the constant airflow also prevents stratification.
  • High volume airflow allows for the reuse of antique, or less efficiently sealed cases.
  • Remote central unit provides silent, invisible protection from up to 500 ft / 160 meters away via an unobtrusive system of pipes and tubes.
  • Designed and manufactured with the best quality industrial components for extreme reliability.
  • Multiple level failsafe systems and self-monitoring diagnostics.
  • User-friendly controls, including accurate and comprehensive electronic readouts.
  • Optional online remote monitoring and control software developed by iq direct.
  • Multi-point Building Management Service connections, and complete data logging options.
  • Maintenance is minimal.
  • Installation is simple and unobtrusive- use with existing or new galleries.
  • Individual cases may be easily added to, or removed from, the system.
  • Portable- unit moves on casters, new mechanical connections are easily supplied; unit may be easily used for alternate applications as needed.

For manual and data sheet see our Download page.