What is ASHRAE Table 4 and how is it applied in Turkish industry?

Table 4 in the ASHRAE HVAC Applications Handbook (Design Indoor Conditions for Various Places, Products, and Processes) is a library of design indoor temperature/RH set points for 180+ processes and spaces, from textile weaving to library archives, operating theatres to hazelnut storage. In Turkish industry, regulation (Ministry of Health, GMP Annex 1, TSE) often gives ranges without fixing a set point; Table 4 fills that gap. NKT engineering takes the Table 4 value as a starting point and then calibrates for Turkish climate (dry winters, humid summer loads), facility geography (elevation, coastal effects) and operational practice (shifts, economiser cycles). The resulting project value is internationally referenced and defensible.

What is the ideal RH set point for textile weaving?

ASHRAE Table 4 lists 24-27°C/70-85% RH for textile weaving; cotton runs at the upper end while wool weaving holds at 60-70%. High RH preserves yarn elasticity, suppresses static and cuts yarn breakage by 30-50%. In practice the set point is product-driven: 75% RH for 50/50 cotton-polyester, 80%+ RH for 100% extra-long-staple cotton. In Bursa cotton-combing references, NKT starts at 24°C/60-65% RH and steps up to 26°C/75% RH on the weaving line. Atomisation (Neptronic SKH) is the high-volume, low-energy answer; the adiabatic cooling it delivers in summer cuts cooling load by 30-40%. Hygroscopic regain feeds directly into yarn revenue sold by kilogram.

Why should the RH between a print room and the paper store differ by 5-8 points?

Paper is hygroscopic; every 1% RH shift produces ≈ 0.03% dimensional change. The print room sits at 24-27°C/43-47% RH (ASHRAE lithographic press), and the paper store sits 5-8 points higher at 50-55% RH. The differential slows moisture loss as stock moves into the press environment and prevents registration errors; in-press heat then drops RH by 3-5 points anyway, so the two spaces equalise during the run. Reverse the gradient and paper picks up moisture, fluctuates and produces four-colour drift. NKT print-shop references deliver independent set points to each room via Neptronic SKE4 resistive steam humidifiers, with stainless hygienic distributors in the paper store. The graduated RH approach is standard procedure across our Konya and Istanbul projects.

What is the legal RH requirement for hospital operating theatres?

In Turkey, the Ministry of Health Inpatient Treatment Institutions Operating Regulation and the Hygienic Class regulation cite ASHRAE Standard 170-2021 for international alignment. For operating theatres the mandatory band is 20-24°C and 20-60% RH, with a 50% target set point. ICUs and delivery rooms run at 21-24°C/30-60% RH; isolation rooms require different pressure-temperature combinations. Below 30% creates static and dry mucosa, above 60% supports microbial growth. Steam must be mineral-free, Neptronic SKS4 steam-to-steam (facility boiler + RO secondary loop) or RO-fed SKE4 units are specified; mineral-laden steam clogs HEPA filters and breaches the hygiene class. NKT hospital projects deliver 24/7 trend logging and band alarms via the BMS.

What RH set point does GMP/cGMP Annex 1 require in pharmaceutical production?

EU GMP Annex 1 (2022 revision) does not mandate a single RH value; it requires per-room validation by manufacturing class. Each room sets its process-specific point via a User Requirement Specification (URS) and risk assessment. The typical range is 20-25°C/30-45% RH. Effervescent tablet and lyophilised manufacturing require <20% RH (combined with a Neptronic dehumidifier); sterile liquid filling caps RH at 45%. Grade A/B/C/D classes encode temperature/RH set points in the specification and monitor HVAC continuously. NKT pharma references use SKS4 steam-to-steam (clean, mineral-free); trend logs are exported for GMP audit. Dew-point control is pushed below +4°C in low-RH zones.

Why is a ±3% RH band critical in museums and archives?

Wood, paper, textile and parchment collection items are hygroscopic; RH swings drive dimensional instability and lead to micro-cracking, joinery failure and colour fade. ASHRAE Table 4 prescribes 21°C/50% RH ±3% for museums, libraries and archives; temperature is secondary, RH stability is the priority. The ±3% band is hard to hold with traditional mineral-steam systems, modulation accuracy and rapid response are required. NKT museum and archive projects pair the Neptronic SKE4 resistive steam humidifier (±1% internal precision) with DDC-controlled high-accuracy sensors; single-pass cycling absorbs seasonal swings independently of latent loads. Display cases are managed as separate zones. Liquid-water atomisation is not used here because of condensation risk on artefact surfaces.

Why is a lithium battery dry room outside the scope of ASHRAE Table 4?

ASHRAE Table 4 expresses set points in relative humidity and bottoms out at 5% RH; a lithium battery dry room is governed by absolute humidity (dew point), with targets of -40°C to -60°C dew point (≈ 1% RH and below). Lithium-ion cell electrolytes are hygroscopic; ambient moisture irreversibly reduces capacity and raises thermal-runaway risk. Dry-room design is therefore its own discipline: silica-gel rotor desiccant dehumidification, multi-stage trains, sub-0.1 ACH envelope tightness, and personnel/material airlocks. As new Turkish gigafactories come online, the NKT engineering team designs them against this separate standard; our lithium-battery dry-room article provides further detail.

What is the optimum temperature and RH band for storing Turkish hazelnuts?

For Turkish hazelnuts (Ordu, Giresun, Trabzon) the optimum is 1-7°C and a 50-60% RH band. Relative humidity above 60% promotes Aspergillus flavus/parasiticus mould growth and the formation of harmful aflatoxins, so keeping RH below 60% is critical. In humid summers (Black Sea climate typically 85-90% outdoor RH), holding the interior within this band requires combined dehumidification and cooling, producing a marked moisture gradient between indoors and outdoors. NKT food-storage projects deliver RH control via a dehumidifier (condensation or silica-gel rotor depending on room temperature) and temperature control via the Neptronic Tarka 360 room thermostat. Hitting the 5-6% kernel moisture target pre-export is critical for Turkish Standard TS 3074 compliance.

Should textile mills use atomisation or steam-based humidification?

Atomisation (pressurised water or high-frequency ultrasonic) is the dominant textile solution because: (1) target RH is high (70-85%) and steam is energy-expensive at that load; (2) atomisation provides adiabatic cooling, dropping summer floor temperature by 4-6°C and shrinking cooling investment; (3) energy use is 85-90% lower than steam. The Neptronic SKH high-pressure atomisation system modulates up to 1,000 kg/h on a single line, holding ±3% RH across multiple nozzles. Steam (SKE4 or SKS4) appears in textile only in precision test labs and hygienic departments. Water quality is critical, RO is the standard; hard water clogs nozzles and emits mineral dust.

How are ASHRAE values adapted for high-altitude facilities in Turkey?

ASHRAE psychrometric charts are drawn for the standard atmospheric pressure of 1013.25 hPa. Erzurum (1,850 m) ≈ 810 hPa, Sivas (1,285 m) ≈ 868 hPa, Erzincan (1,215 m) ≈ 874 hPa. At lower pressure the same RH represents higher absolute humidity; air is less dense, mass flow falls and the humidification load deviates 5-10% from standard calculations. Correction: solve the psychrometric equations at the site pressure, or apply an altitude factor (≈ 0.012/100 m). Temperature values from ASHRAE Table 4 are altitude-independent, but the water-vapour mass calculation requires correction. The NKT Pro calculator models site pressure automatically; a manual calculation from the 1013 hPa table systematically under-sizes high-altitude installations such as Erzurum by 5-8%.

Reference Guide52 min read

Sectoral Relative Humidity Design Conditions Guide, ASHRAE Table 4 Adapted for Türkiye Industry

Q: Why is a ±3% RH band critical in museums and archives?

Wood, paper, textile and parchment collection items are hygroscopic; RH swings drive dimensional instability and lead to micro-cracking, joinery failure and colour fade. ASHRAE Table 4 prescribes 21°C/50% RH ±3% for museums, libraries and archives; temperature is secondary, RH stability is the priority. The ±3% band is hard to hold with traditional mineral-steam systems, modulation accuracy and rapid response are required. NKT museum and archive projects pair the Neptronic SKE4 resistive steam humidifier (±1% internal precision) with DDC-controlled high-accuracy sensors; single-pass cycling absorbs seasonal swings independently of latent loads. Display cases are managed as separate zones. Liquid-water atomisation is not used here because of condensation risk on artefact surfaces.

Q: Why is a lithium battery dry room outside the scope of ASHRAE Table 4?

ASHRAE Table 4 expresses set points in relative humidity and bottoms out at 5% RH; a lithium battery dry room is governed by absolute humidity (dew point), with targets of -40°C to -60°C dew point (≈ 1% RH and below). Lithium-ion cell electrolytes are hygroscopic; ambient moisture irreversibly reduces capacity and raises thermal-runaway risk. Dry-room design is therefore its own discipline: silica-gel rotor desiccant dehumidification, multi-stage trains, sub-0.1 ACH envelope tightness, and personnel/material airlocks. As new Turkish gigafactories come online, the NKT engineering team designs them against this separate standard; our lithium-battery dry-room article provides further detail.

Q: What is the optimum temperature and RH band for storing Turkish hazelnuts?

For Turkish hazelnuts (Ordu, Giresun, Trabzon) the optimum is 1-7°C and a 50-60% RH band. Relative humidity above 60% promotes Aspergillus flavus/parasiticus mould growth and the formation of harmful aflatoxins, so keeping RH below 60% is critical. In humid summers (Black Sea climate typically 85-90% outdoor RH), holding the interior within this band requires combined dehumidification and cooling, producing a marked moisture gradient between indoors and outdoors. NKT food-storage projects deliver RH control via a dehumidifier (condensation or silica-gel rotor depending on room temperature) and temperature control via the Neptronic Tarka 360 room thermostat. Hitting the 5-6% kernel moisture target pre-export is critical for Turkish Standard TS 3074 compliance.

Q: Should textile mills use atomisation or steam-based humidification?

Atomisation (pressurised water or high-frequency ultrasonic) is the dominant textile solution because: (1) target RH is high (70-85%) and steam is energy-expensive at that load; (2) atomisation provides adiabatic cooling, dropping summer floor temperature by 4-6°C and shrinking cooling investment; (3) energy use is 85-90% lower than steam. The Neptronic SKH high-pressure atomisation system modulates up to 1,000 kg/h on a single line, holding ±3% RH across multiple nozzles. Steam (SKE4 or SKS4) appears in textile only in precision test labs and hygienic departments. Water quality is critical, RO is the standard; hard water clogs nozzles and emits mineral dust.

Q: How are ASHRAE values adapted for high-altitude facilities in Turkey?

ASHRAE psychrometric charts are drawn for the standard atmospheric pressure of 1013.25 hPa. Erzurum (1,850 m) ≈ 810 hPa, Sivas (1,285 m) ≈ 868 hPa, Erzincan (1,215 m) ≈ 874 hPa. At lower pressure the same RH represents higher absolute humidity; air is less dense, mass flow falls and the humidification load deviates 5-10% from standard calculations. Correction: solve the psychrometric equations at the site pressure, or apply an altitude factor (≈ 0.012/100 m). Temperature values from ASHRAE Table 4 are altitude-independent, but the water-vapour mass calculation requires correction. The NKT Pro calculator models site pressure automatically; a manual calculation from the 1013 hPa table systematically under-sizes high-altitude installations such as Erzurum by 5-8%.

A Türkiye-industry adaptation of the ASHRAE HVAC Applications Handbook Table 4: full design-condition tables (temperature + relative humidity) for food & beverage, textiles, printing, pharmaceuticals, electronics, museums & archives, raw material storage, plastics & rubber, and tobacco/leather sectors.

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Related Glossary Terms

For deeper definitions of the technical concepts in this article, browse the related entries in the NKT Glossary:

Relative Humidity (RH)Absolute Humidity Dew Point Enthalpy Dry Room Cleanroom Sugar Bloom BMS (Building Management System)Calibration ESD (Electrostatic Discharge)HVAC (Heating, Ventilation & Air Conditioning)GMP (Good Manufacturing Practice)ASHRAE (American Society of Heating, Refrigerating and AC Engineers)ACH (Air Changes per Hour)High-Pressure Atomization Steam Humidification Adiabatic Humidification Hygienic Steam HACCP (Hazard Analysis & Critical Control Points)ICH Q1A (Pharmaceutical Stability Standard)ISO 14644 (Cleanroom Classification)MSL (Moisture Sensitivity Level)Hygroscopic (Moisture-Attracting)Sorption (Adsorption + Absorption)PVB (Polyvinyl Butyral)Fat Bloom Tempering (Chocolate Crystallization)Water Activity (aw)Brix (°Bx)Case Hardening Hygroscopic Regain Static Electricity Natural Ventilation Design Conditions (Set Point)Resistive Steam Humidifier Indoor Air Quality (IAQ)Humidification Capacity (kg/h)Silica (SiO₂)Evaporative Cooling (Adiabatic Cooling)Modulation (Capacity Modulation)

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