MARK Climate Technology distributor in TürkiyeElburz Mühendislik
CALFLO process and make-up air
Controlled, heated outdoor air to replace air removed by extract systems. A MARK solution for blasting, welding and processes with high ventilation requirements.
How does CALFLO work?
CALFLO heats outdoor air with a directly gas-fired burner before supplying it to the facility. The burner and flame sit within the airstream, so combustion products enter the supply air. This distinguishes it from indirect-fired equipment that separates combustion gases through a heat exchanger and flue.
Its role in the system
It provides a controlled replacement-air supply for facilities with substantial extraction. Heated make-up air helps reduce the effect of cold incoming air on winter working conditions. Air distribution and the required room pressure are considered together with the extract system.
Blasting and welding areas in a shipyard
Illustrative application scenario; not a completed Elburz project.
The need
A shipyard workshop wants to control the volume and temperature of incoming outdoor air while process extraction is operating.
The assessment
Extract airflow, target room pressure, outdoor conditions and required supply-air temperature are considered together.
The approach
Where project suitability is confirmed, CALFLO supplies heated make-up air. Process extraction and contaminant capture are designed separately.
The basic airflow principle
- 01Outdoor air
- 02Heating by CALFLO
- 03Working area
- 04Process extraction
Schematic illustration. Supply and extract volumes are determined by the required pressure balance; they do not have to be equal in every project.
CALFLO technical data
| Nominal heat input | 64–896 kW; manufacturer’s series range on a lower-heating-value basis. |
|---|---|
| Burner turndown | 20:1; burner capacity adjustment, not a fan airflow ratio. |
| Airflow · ΔT 35 K | 5,430–76,080 m³/h; manufacturer’s table references 15 °C. |
| Airflow · ΔT 55 K | 3,500–48,700 m³/h; manufacturer’s table references 15 °C. |
| Burner construction | Modulating stainless steel line or box burner. |
| Casing | Seawater-resistant AlMg3 aluminium; single or double skin. |
| Installation | Indoor or outdoor configurations. |
| Filtration | Optional HT filters; filter grade and scope are project-specific. |
ΔT is the air temperature rise, not the absolute supply temperature. Airflow ranges span different models and fan selections. Final duty is verified against duct pressure, filters, outdoor conditions and required supply temperature.
How airflow affects heating duty
At the same temperature rise, more outdoor air requires more heating power. Make-up airflow and the outdoor-to-supply temperature difference therefore matter more to CALFLO selection than floor area alone.
Approximation: Q = 0.000335 × airflow (m³/h) × temperature rise (K). Assumes air density of 1.2 kg/m³ and specific heat of 1.005 kJ/(kg·K).
This illustrates the relationship; it is not a unit selection or gas consumption calculation. Building heat loss, process loads and actual design conditions require separate assessment.
Controls and operation
Heat input, fan operation and facility extraction involve different control functions. Burner turndown does not mean the entire system varies its airflow by the same ratio.
Fan and time-schedule options
The manufacturer’s brochure lists C10/C12 for on/off fan operation and C20/C22 for high/low operation. C12 and C22 include a clock. Panels and site connections depend on the quotation scope.
Coordination with extraction
Make-up air operation is coordinated with the relevant extraction and process schedule. Target room pressure and necessary interlocks are defined in the project controls; these are not assumed to be standard on every unit.
Maintenance access
Space is required to service filters, fans, the burner and gas equipment. Maintenance intervals follow the manufacturer’s instructions, operating hours and site conditions.
Frequently asked questions
Can it be used in a paint shop?
A paint shop first requires a controlled air supply to replace the extracted air. With CALFLO’s direct firing, combustion products and added moisture must be assessed for compatibility with the coating process. Solvent areas, unit location and required air quality need project-specific suitability confirmation from MARK; ATEX suitability must not be assumed for a standard CALFLO.
Is CALFLO an extract or dust collection system?
No. CALFLO is considered on the make-up air side. Capturing dust, fumes or vapours at source and extracting them are the functions of separate systems.
Can it be added to an existing facility?
This is assessed by reviewing the existing extract system, air inlets, energy supply and controls. Unit selection is not based on floor area alone.
Does CALFLO cool or dehumidify the air?
The CALFLO described here is a gas-fired air heating solution. Cooling or dehumidification, where needed, requires separate design provision.
Do HT filters capture process dust or solvents?
The HT filter option does not replace process exhaust treatment. Supply-air filtration and source capture of dust, fumes or solvents serve separate functions.
An initial assessment for your project
Share your application and the project information you have. If some values are not yet known, we can start with an existing specification or extract-unit details.
Elburz coordinates product selection and quotation scope with MARK. Equipment, controls, installation and commissioning scope are clearly stated in the quotation.
- Process type and facility location
- Existing or required extract / make-up airflow
- Required indoor and supply-air temperatures
- Duct, filter and other pressure losses; drawings if available
- Gas and electrical supply, installation space and operating hours
Technical source and documents
Product features are based on MARK’s CALFLO page. The brochure and original technical manual are available through the manufacturer’s page.
Source checked: 26 September 2026. The application scenario is an illustrative example prepared by Elburz; it does not promise a specific performance or saving.
Let’s discuss your project
Share your application and project requirements. We coordinate product selection, quotation and supply with MARK.