A mehana is priced like a tavern and engineered like a grill house: a charcoal bed running at 900-1,100 °C, a menu built on mince kebabs and skewers that drip fat straight onto the coals, and a dining room that in most Sofia and Plovdiv buildings sits directly beneath somebody’s living-room window. Bulgarian approval for that kitchen turns on three measurable things – capture at the hood, transport velocity inside the duct, and odour concentration at the receptor – plus a quotation that states all three in the same units the acceptance test will use. This guide gives the numbers to demand, runs the sizing arithmetic on a typical cookline, and lists the clauses that decide whether the file passes or comes back.
1. Why the charcoal grill sets the specification, not the fryer
Bulgarian menu engineering concentrates the load in one place. A working mehana kitchen usually runs four appliances: a charcoal grill of 1.5-2.5 m, a fryer for potatoes and breaded cheese, a two- or four-burner range for stews and soups, and a cold prep area. The fryer produces the visible volume of oil mist. The grill produces the mass that never quite leaves the air.
Three mechanisms drive that. First, fat pyrolysis: when dripping fat lands on coals at 900-1,100 °C it cracks into aldehydes, ketones and polycyclic aromatic hydrocarbons, and a large share of that material is bound to particles below 0.1 micron. Second, ash and soot carry-over from the bed itself, which is why a charcoal plume reads grey rather than white. Third, water vapour: mince at 60-70% moisture flashes off and condenses on the cooler first metre of duct, and the condensate binds grease into a film that thickens far faster than the fryer side ever manages.
The procurement consequence is blunt. A mesh or baffle filter removes droplets above roughly 10 micron, which is the part you can see. Around 60-80% of the mass in a charcoal plume sits below 1 micron and passes through a mesh filter almost untouched. A quotation priced as “hood plus filter plus fan” is therefore a quotation for the visible plume only – the sub-micron fraction leaves the roof and arrives at the nearest openable window as odour, which is the complaint that actually gets inspected.
Practical test: ask the supplier which treatment stage removes the fraction below 1 micron, and ask for the pressure drop that stage adds at your design airflow. A quote that answers “the filter catches the grease” has answered a different question.
2. Three numbers a Bulgarian quote usually leaves out
Across the quotations that reach Bulgarian operators, the same three parameters go missing. None of them is exotic; all three are cheap to state and expensive to discover after installation.
2.1 Hood overhang and the capture envelope
Capture is geometry before it is airflow. The canopy should overhang the appliance by 150-200 mm on each open side, and the front edge should sit about 50 mm proud of the appliance face. A 2 m charcoal grill under a 2 m canopy has zero overhang: the plume rolls off the front edge at the first gust from a door, and no amount of extra fan capacity recovers it. Side panels on an end-of-run hood do more for capture than 15% more airflow, and they cost a fraction of it.
2.2 Transport velocity inside the duct
Grease-laden vapour has to stay airborne until it reaches the treatment stage. Design transport velocity for a charcoal duty is 10 m/s, with 8 m/s as the absolute floor on a short, clean, vertical run. Below that, grease settles on the duct floor, and the deposit becomes a fire load and an inspection finding rather than a maintenance nuisance. A quote that specifies duct diameter but not velocity has skipped the number that governs both.
2.3 Pressure at the duty point, not the fan’s maximum
Catalogues quote a maximum static pressure at zero flow. What matters is the pressure the fan produces at your design airflow, after the hood, the filters, the treatment stages, the silencer, the louvre and every elbow. A fan rated at 1,000 Pa maximum, running at 850 Pa at duty, has 15% in reserve and is honestly sized. A fan rated at 1,000 Pa maximum that the design asks to deliver 1,150 Pa will simply move less air, and the commissioning reading will be short by 20-30% with no obvious cause.
3. Sizing a mehana cookline: a worked example you can copy
Take a mid-size mehana in Sofia: a 2.0 m charcoal grill with an open front, a 0.7 m single-vat fryer, and a 1.2 m two-burner range for stews. The per-metre method used across the trade starts from 2,000 m³/h for each metre of hood, rises to 2,500 m³/h per metre for an open charcoal or display front, and uses roughly 4,000 m³/h per burner where burners are the better unit of count.
- Charcoal grill, 2.0 m at 2,500 m³/h per metre = 5,000 m³/h
- Fryer, 0.7 m at 2,000 m³/h per metre = 1,400 m³/h
- Stew range, 1.2 m at 1,500 m³/h per metre = 1,800 m³/h
- Subtotal 8,200 m³/h; add 10% margin = 9,000 m³/h at the hood
Now cross-check the same cookline by face velocity, because the two methods disagree often enough to be worth running both. A 3.9 m canopy with a 1.0 m deep aperture has 3.9 m² of open face. At 9,000 m³/h that is 2.5 m³/s, or 0.64 m/s across the face. For an open charcoal front, 0.5-0.7 m/s is the working band; a wall-mounted hood with side panels can drop to 0.35-0.5 m/s. If the face-velocity figure comes out below 0.4 m/s on a charcoal duty, the hood is too big for its airflow and the plume will escape at the ends – shorten the canopy or raise the airflow.
Duct sizing follows from the velocity target. At 10 m/s, 2.5 m³/s needs 0.25 m² of cross-section, which is a 560 mm diameter. Round up to 600 mm and the velocity falls to about 8.8 m/s – still above the floor, with a little room for a future grease layer. That is the point where the arithmetic stops being abstract: the duct diameter is not a preference, it is the output of the velocity decision.
The pressure budget then reads roughly as follows on a 20 m run with four elbows: hood entry and face losses about 40 Pa, mesh filter 60 Pa, electrostatic stage 120 Pa, carbon stage 180 Pa, straight duct friction around 30 Pa, four elbows near 180 Pa, silencer 60 Pa, outlet louvre 40 Pa. Total approximately 710 Pa, so specify a fan that delivers 9,000 m³/h at 800-900 Pa rather than one whose headline maximum happens to be 900 Pa. Where the building has a duct and roof access, that calculation lands on the ducted end of the range – an electrostatic precipitator module plus a matched centrifugal fan, documented as a system rather than as two separate purchases, which is how the ducted ESP purifier range is specified.
3.1 Converting pressure to motor size
Fan shaft power is airflow in m³/s multiplied by pressure in pascals, divided by total efficiency – typically 0.60-0.65 for a belt-driven centrifugal unit at this size. At 2.5 m³/s and 900 Pa: 2.5 x 900 / 0.62 = 3,630 W of shaft power, which calls for a 4 kW motor with a small reserve, or 5.5 kW where the client wants headroom for a dirty filter. A quote offering 3 kW against that duty is not a bargain; it is a fan that will run at the end of its curve, overheat in summer and deliver less air than the commissioning sheet requires.
Altitude is the last correction, and Bulgaria is not flat. Sofia sits at about 550 m, Plovdiv at 160 m, Bansko at 936 m. Air density falls from 1.20 kg/m³ at sea level to roughly 1.14 kg/m³ in Sofia on a warm day. A fan curve published at standard density therefore delivers about 4-6% less pressure at the same speed in Sofia, and more in Bansko. Ask whether the curve is at 1.2 kg/m³ and, if the site is above 500 m, add the correction to the pressure budget rather than discovering it at handover.
4. What the odour complaint actually measures
Odour is judged where people are, not where the fan is. The characteristic Bulgarian case is a ground-floor mehana in a panel block: the kitchen opens onto the courtyard, residents live 6-9 m above with windows 10-15 m horizontally from the outlet, and the complaint arrives on a still evening in the heating season when every window is shut and the courtyard air turns over slowly. An outlet discharging at roof level, above the eaves line and away from the courtyard face, changes the outcome more than any single treatment upgrade.
The legal frame is layered rather than single. The Clean Air Act (Zakon za chistotata na atmosferniya vazduh), in its consolidated version to State Gazette No. 78 of 2025, sets the ambient-air regime and the emission obligations; the regional health inspectorate (RZI) acts on health-related complaints about premises; the regional inspectorate of environment and waters (RIEW) handles installations within its permitting scope; and municipal ordinances on public order cover the nuisance end of the same problem, particularly for late trading and courtyard discharge. In practice an operator faces a complaint-driven inspection, so the file that matters is the one you can produce on the day: design airflow, treatment stages, cleaning records, and a measurement taken at the outlet.
Where an odour assessment is commissioned, it follows EN 13725 dynamic olfactometry and reports in European odour units per cubic metre (ouE/m³). The benchmark values that appear in European assessments are around 1 ouE/m³ at the receptor – the nearest dwelling window – and 5 ouE/m³ at the site boundary. Those figures are worth knowing before a supplier promises “no smell”: they are concentrations, not adjectives, and a two-stage electrostatic plus carbon system is designed to reach them at the receptor, not at the fan inlet.
Grease deposition is measured separately and has hard numbers. EN 15780:2025 Annex J sets the working frame used in European duct cleaning: an average deposit of no more than 200 micron, a single-point reading above 500 micron triggering immediate cleaning, and access panels at intervals no greater than 2 m so that the readings can actually be taken. A mehana on charcoal will reach the 500 micron trigger faster than a fryer-only kitchen because of the ash fraction, so the cleaning interval should be set from a first inspection at three months rather than from a generic annual schedule.
Measurement point discipline: sample 1 m downstream of the last treatment stage, at the centre of the duct, with the system at design airflow. Readings taken at the fan inlet, or with the kitchen half-idle, are the commonest reason two reports on the same system disagree by a factor of three.
5. Ductless, ducted, or split: the three routes in a Bulgarian building
Building constraints in Sofia and Plovdiv narrow the choice quickly. The wider centre contains protected zones where a new roof penetration or a changed facade needs consent that can take a season; upper floors of residential blocks have no available riser; and ground-floor premises often have 2.3-2.5 m of clear height once services are boxed in. Each of those constraints maps to a different architecture, and the decision should be made before the quotation is requested rather than after.
5.1 No penetration, no riser: recirculating purification
Where the roof cannot be touched and the facade cannot change, the workable route is a ductless hood that treats and returns air to the room: a multi-stage electrostatic cell for the sub-micron fraction, followed by an activated carbon stage for the gas phase, with the return air delivered away from the cook. This is the mainstream answer for mehana fit-outs in protected buildings and for premises under residential floors, and it is the architecture behind the ductless range hood family. Two caveats belong in the contract: the carbon stage is a consumable with a defined replacement interval, and a recirculating system is not an exemption from odour obligations, because the room air it returns still has to be clean enough that the courtyard does not smell of grill.
5.2 Duct and roof available: ducted treatment
Where a riser exists and the roof is accessible, ducted treatment is the lower-risk option on a heavy charcoal load: capture at the hood, transport at 10 m/s, electrostatic precipitation and carbon before the discharge point, with the outlet placed above the eaves and away from the courtyard face. It costs more in installation and less in operating surprises, and it moves the discharge to a height where dilution does the remaining work.
5.3 Low clear height: split the cabinet from the canopy
When there is no room for a vertical component above the hood – the classic 2.4 m ground-floor fit-out, or a heritage interior where the ceiling line cannot be lowered – the purification cabinet can be decoupled from the canopy entirely. A shallow canopy captures, a short duct carries the vapour at velocity, and a floor-standing cabinet 520 mm wide stands behind the cookline, in a back-of-house recess, or in an adjacent plant space. No vertical stack, no roof penetration, and the cabinet can be serviced from the floor rather than from a ladder.
5.4 No fixed cookline: mobile and terrace service
Mehana operators increasingly run a second point of sale – a market stall, a festival pitch, a summer terrace grill – where nothing can be built in. Self-contained ventless carts solve that case, and the ventilation decision reduces to matching the hood to the menu: a plancha or fryer menu needs far less than an open charcoal grill. The ventless catering cart range exists for exactly that duty, and the sizing logic in section 3 still applies, just at a smaller scale.
6. Reading the quotation line by line, now that prices are in euro
Bulgaria adopted the euro on 1 January 2026 at the fixed rate of 1.95583 lev per euro, with the lev ceasing to be sole legal tender on 1 February 2026 and compulsory dual display running to 8 August 2026. For equipment purchasing this changes two things that matter at signature: the currency of the price and the currency of the escalation clause.
- Currency and date. A quotation still written in lev in late 2026 is either an old document or a supplier working from an old template; ask for a euro price with a stated validity date. Imported equipment is bought in euro or US dollars, so a lev-denominated price carries a conversion the buyer cannot audit.
- Validity and escalation. Ninety days is normal for European equipment; thirty days is a pressure tactic. If the validity is shorter than the delivery lead time, the escalation clause is doing the real pricing, so read what index it references and whether it is capped.
- Incoterms. DAP Sofia and EXW Guangdong are not the same offer. DAP puts delivery and import clearance risk on the seller up to the named place; EXW leaves the buyer with export clearance, freight, duty and the 20% Bulgarian VAT recovery process. The gap is usually 8-15% of the equipment value, and it is the single line most often left blank.
- Excluded works. Confirm in writing who provides the crane or scaffold for roof plant, who runs the 400 V three-phase supply to the fan isolator, who cuts and waterproofs the roof penetration, who supplies make-up air, and who pays for the electrical inspection.
- Warranty scope. Twelve months on the whole unit is the norm. Wear items – electrostatic cell, aluminium collector plates, sealing strips, ceramic insulators, carbon media – are typically excluded, so get the wear-item list and the expected replacement interval written into the contract rather than discovered at the first claim.
- Documentation. For the occupancy certificate under the Spatial Development Act, the file needs the CE declaration of conformity, instructions in Bulgarian, the electrical and fire-safety documentation, and the commissioning protocol. Ask which of those the supplier provides and which the installer must generate.
7. The ten-point acceptance sheet
Print this and take it to handover. Every item is measurable on site with a balometer or an anemometer, a manometer and a thermometer, and none of it depends on the supplier’s own opinion.
- Measured airflow at the hood face within plus or minus 10% of the design figure of 9,000 m³/h.
- Face velocity across the canopy aperture in the 0.5-0.7 m/s band for an open charcoal front.
- Duct velocity at the design point at or above 10 m/s, verified by pitot traverse or from measured airflow and a confirmed internal diameter.
- Fan static pressure at duty within 10% of the calculated 800-900 Pa, with the filters and treatment stages in place and clean.
- Motor current draw within the nameplate rating, on all three phases, at design airflow.
- No visible plume at the discharge under full grill load, checked after 30 minutes of peak cooking rather than at start-up.
- Smoke test on every duct joint and access panel, with no leakage at the flanges.
- Access panels present at intervals no greater than 2 m, each openable without tools and sealed with a grease-resistant gasket.
- Noise at the nearest dwelling facade within the residential band of 55 dB(A) day and 45 dB(A) night, measured with the kitchen at peak.
- Written cleaning interval and a first inspection date, derived from the EN 15780 deposit readings rather than from a default annual cycle.
8. Five-year running cost, without the sales deck
Operating cost on a charcoal duty has three components and only one of them is electricity. Take the worked example: a 4 kW fan running 3,000 hours a year draws about 12,000 kWh. At the non-household price band Bulgarian businesses have faced since market liberalisation – roughly 0.15-0.25 euro per kWh depending on contract – that is 1,800-3,000 euro a year, and the fan is the smaller half of the story.
The carbon stage is the item that surprises buyers. At 9,000 m³/h with a 0.3 second residence time, the bed volume is 0.75 m³; at a bulk density of 450-480 kg/m³ that is roughly 350 kg of media. On a heavy charcoal load, with the grill running six days a week, annual replacement is realistic, and the media cost plus the labour to change it typically exceeds the fan’s electricity bill. A quotation that shows a carbon stage but no replacement interval has not priced the five-year cost.
Cleaning labour is the third component. A duct on charcoal duty will hit the 500 micron single-point trigger sooner than a fryer-only duct, so budget four to six professional cleans in five years and one access-panel reseal, rather than a single annual visit priced on the assumption that nothing changes. Add the wear items from section 6 and the honest five-year comparison between ductless and ducted usually comes out closer than the capital-cost difference suggests – the ducted option wins on running cost and loses on installation, and the crossover depends on whether the building already has a riser.
9. What the design response looks like
Read against sections 1 to 8, the specification that survives a Bulgarian mehana fit-out is not complicated: capture geometry with real overhang, a transport velocity that keeps grease airborne, a treatment train that addresses the sub-micron and gas phases rather than only the visible droplets, and a pressure budget that survives a dirty filter.
For a charcoal-led menu with no roof access, the appropriate response is a heavy-fume recirculating hood built around a multi-stage electrostatic cell, paired with a separate odour stage so that the carbon can be replaced without touching the precipitator – which is how Souniny configures the ND-series with an odour tower. Where headroom rules out anything above the canopy, a floor-standing cabinet at 520 mm width decouples purification from the hood and leaves the ceiling line untouched. Where a riser and roof are available, the same treatment stages move into a ducted train behind an electrostatic precipitator module with a matched centrifugal fan, and the discharge goes above the eaves. For the terrace and the festival pitch, a self-contained cart carries its own stage.
What ties those four answers together is not the hardware but the paperwork: a stated design airflow, a stated pressure at duty, a stated odour target at the receptor, and a cleaning interval derived from measurement. A mehana that can produce those four numbers on the day an inspector calls has already solved the problem the equipment was bought for, and the twelve-month whole-unit warranty that Souniny issues is only useful once the wear-item list and the commissioning protocol sit beside it in the same file.
