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

This reference guide is the Turkish-industry-adapted, English-language edition of Table 4, Design Indoor Conditions for Various Places, Products, and Processes from the ASHRAE HVAC Applications Handbook. For each sector it provides the indoor design temperature and relative humidity set point, process-level sub-applications, and critical control notes. For mechanical engineers, it is the primary reference for the equipment sizing step; for production and quality teams, it is the starting point for defining indoor set points. The NKT – Nem Kontrol Teknolojileri team has enriched the guide with additional notes relevant to equipment selection — sector-specific NKT notes on print, textile, food, pharmaceutical, museum, lithium battery and electronics manufacturing appear under each topic. All calculations from this guide can be performed in seconds with the NKT Pro mobile application, and the sector-selection assistant routes you to the right Neptronic device. The intent of the guide is two-fold: to provide the input data for engineering design, and to act as a reference document that ends set-point arguments during commissioning.

How to Use This Guide

Used correctly, the sectoral design-conditions guide serves three main functions. First, as the input data for engineering design. In a new facility, or in the retrofit project of an existing one, the sectoral set point is the very first step — without it neither the load calculation nor equipment sizing can proceed. Second, as preparation for audits and certification. The HACCP plan, GMP audit, ISO 22000 certification process, TİTCK inspection, FDA inspection — all of these processes require the design condition as a written specification. The sectoral guide is the tangible document showing which standard you reference and why the chosen set point was selected. Third, at commissioning and performance verification. After commissioning, does the ambient condition stabilize and meet the table over the long run? Sectoral reference values are the continuous comparison baseline that answers this question. In all three roles, no single table is enough on its own — each of the 9 sector groups below must be evaluated together with its process needs, regulatory framework and Türkiye field experience.

About ASHRAE Table 4 and the Türkiye Adaptation

The ASHRAE HVAC Applications Handbook is updated every four years by the American ASHRAE society; Table 4 lives in the Industrial Air Conditioning chapter. Its values rest on decades of international research, manufacturer feedback and field observation. That said, ASHRAE values default to North American conditions — product-quality standards, average climate, atmospheric pressure and operator practice can differ in nuance. In Turkish industry, local adaptation is required especially for (a) Turkish (Oriental-type) tobacco, (b) hazelnut (Black Sea hazelnut), (c) traditional cheeses (kashar, tulum, beyaz peynir), (d) historic-building / museum conditions, and (e) high-altitude facilities (Erzurum 1,850 m, Konya 1,020 m, Kayseri 1,050 m). This guide is the English-language, Türkiye-industry-adapted edition of ASHRAE Table 4, with references to Turkish standards (Turkish Food Codex Notifications, TS EN norms, TS 825 climate zones) where applicable.

Food and Beverage Manufacturing

Food and beverage manufacturing is one of the broadest industry segments in Türkiye. Each sub-process requires its own relative humidity (RH) level; the table below covers the main production lines for bread, dough, brewing, candy, chocolate, cheese, mushrooms, meat and fish, and fruit storage. When choosing design conditions, not only process yield, but also water activity (a_w), microbial safety (HACCP) and Turkish Food Codex requirements must be observed. In food lines, the stability of room moisture matters as much as the average set point; a ±3% RH band is typically targeted.

Textiles and Garment Manufacturing

Textile is Türkiye's traditional export workhorse. To preserve the natural moisture balance of fibers and to prevent yarn breakage and static electricity, the sector requires high relative humidity. The hygroscopic behavior of cotton, wool and synthetic fibers differs significantly: cotton and wool readily absorb ambient moisture, while synthetic fibers (polyester, nylon) require RH for static-charge balance more than surface moisture. The table below lists every step of textile production by fiber type, in line with ASHRAE Table 4.

Printing and Graphic Arts

The printing industry relies on stable relative humidity because of the hygroscopic nature of paper. Paper loses dimensional stability with even ±2% RH excursions; this causes color registration errors, curl, static electricity and ink-transfer issues. The table below presents the printing-and-graphic-arts section of ASHRAE Table 4 in English with NKT field notes.

The RH delta between the paper-storage room and the press room dramatically influences paper performance during printing. The ASHRAE convention is to hold the paper-storage RH 5–8 points above the press room; this delta lets newly-arrived paper gradually equilibrate before entering the press. Without it, paper absorbs or releases moisture during printing — causing grain-direction curl, ink spread and static issues. For a detailed worked example see Humidification Load Calculation — Konya climate example.

Pharmaceutical and Healthcare Facilities

Pharmaceutical manufacturing and healthcare facilities sit at the tightest end of the RH-control spectrum. GMP (Good Manufacturing Practice), cGMP Annex 1, ICH Q1A stability testing, ASHRAE Standard 170 (ventilation of health-care facilities) and ISO 14644 cleanroom standards form the regulatory frame of set-point selection. In Türkiye, the Turkish Medicines and Medical Devices Agency (TİTCK) audits cite these standards directly. The table below lists typical design conditions for pharmaceutical production lines.

Electronics and Precision Manufacturing

Electronics manufacturing lives at the intersection of static-electricity (ESD) management, moisture-sensitive components (MSL) and cleanroom classification. The ASHRAE Table 4 sections for electrical products and cleanrooms span design conditions from micro-electronics to high-power systems. In high-precision production areas, holding ambient moisture within ±2% RH is critical both for static control and component moisture absorption. Applications requiring very low dew points (such as the lithium-battery dry room) sit beyond this section in their own category.

Museums, Archives and Libraries

For paper, leather, wood, textile and metal artifacts, RH stability matters at least as much as the average set point. ASHRAE Class A / B / C / D classification governs long-term archival storage; Class A collections require stable protection within ±5% RH. Temperature is secondary but still relevant: thermal expansion/contraction cycles stress glue and bonding lines. The table below presents the museum/archive section of ASHRAE Table 4.

The most critical figure for long-term preservation is the ±3% RH band; wider excursions cause dimensional damage, micro-cracks and fatigue in organic materials (wood, leather, glue). For this reason, controller resolution, sensor placement and control strategy of the humidifier matter at least as much as nominal capacity in museum and archive applications. The gold-standard target for museum environments is an average RH of 50% with day-night and seasonal variation held within ±3%.

Raw Material and Component Storage

Raw-material storage stabilizes ingredient input into production lines and underpins dosing and blending precision. The ASHRAE Table 4 raw-material-storage section covers typical commodities — nuts, chocolate, butter, dates, corn syrup, tea — and their storage design conditions. Hazelnut, one of Türkiye's traditional exports, is a major sub-application of this section.

Plastics and Rubber Manufacturing

The plastics and rubber industry needs RH control both on the production line and in raw-material storage because of polymer feedstocks' moisture sensitivity. Engineering plastics — PA (nylon), PET, PC, ABS — are hygroscopic; they absorb ambient moisture, and when wet material is melt-processed the polymer chains break by hydrolysis — causing surface bubbles, flow marks and mechanical-strength loss during injection molding. For rubber products, vulcanization is also moisture-sensitive.

In plastic production, RH control matters both for raw-material stabilization and for finished-product quality. Drying polymer pellets to below the material-specific maximum processing moisture (e.g. 0.02% for PC, 0.20% for PA6) before injection (residence-time dependent) directly determines surface quality and mechanical strength. For detailed process analysis, see our use of dehumidifiers in plastic production guide.

Tobacco, Leather and Miscellaneous Industries

This section covers the ASHRAE Table 4 entries for tobacco, leather, matches, paint, distilling, gum, abrasive, recreation and general comfort applications. The common thread of these sectors is that ambient moisture is interwoven with the material-conditioning process itself.

From Table to Calculation: In Seconds with NKT Pro

The sectoral design conditions in this guide are only the input data for engineering design. To bring the table to life on site, follow this 4-step discipline:

1. Select the sector + sub-application row — Identify the exact process step in the table (e.g., "Textiles — Cotton Spinning").
2. Read the temperature + RH set point — These define the indoor design condition (value B in the Humidification Load Calculation guide).
3. Apply the humidification load calculation — Use the L = (B − D) × V formula from the Humidification Load Calculation guide to compute hourly load.
4. Add a safety margin to the device capacity — Apply a 15–25% service margin to the calculated load; the result gives the nominal capacity of the humidifier/dehumidifier to be selected.

NKT Engineering Tools — Quick Access

To process the sectoral design conditions in this guide, use NKT's free web-based engineering tools:

• Humidification Load Calculation Guide — Step-by-step bridge from design conditions to kg/h load.
• Psychrometric Calculator — From temperature + RH inputs: dew point, absolute humidity, enthalpy, wet bulb, vapor pressure, specific volume.
• Industrial Dehumidification Calculator — Dehumidifier capacity sized to sectoral design conditions.
• Air Mixing Calculator — Output temperature and humidity for a mixing box.
• Engineering Unit Converter — SI ↔ imperial, kg/h ↔ lb/hr, °C ↔ °F, Pa ↔ psi.
• Humidification Capacity Calculator — Humidifier-capacity sizing.
• NKT Pro Mobile App — Fast on-site report, device-selection assistant, PDF delivery from your phone.
• Contact NKT — Request support in selecting equipment for your sector.

Matching Set-Point Band with Control Precision

The set point you read in the table is only the average value; the second critical design parameter is the tolerance band (e.g. ±2% RH vs. ±5% RH). Band width directly determines the device technology and control strategy. The guide below summarizes the typical tolerance bands for sectoral applications and the corresponding device-technology recommendation:

Defining the tolerance band depends on more than process needs alone — sensor placement, number of measurement points and sensor calibration discipline must also be taken into account. In a single-point system, even if the target band is ±2%, local fluctuations in the space (door openings, machine load, airflow pattern) can be ±4% or wider. In critical applications, collecting data from several points (e.g. 3–5) and using an average or worst-point control strategy is recommended.

Neptronic Humidification Family

Starting from sectoral design conditions, the device(s) you select will fall into one or more Neptronic product families depending on your process RH band and accuracy. As NKT – Nem Kontrol Teknolojileri, we are the authorised Turkish distributor of Neptronic; we provide equipment supply, technical support in equipment selection, technical service and spare parts.

Neptronic

Humidifier Product Family

Steam (SKE4 resistive / SKS4 steam-to-steam / SKG4 gas-fired), atomization (SKH) and evaporative technologies covering every RH band — food, textile, print, hospital, museum, pharma and data center applications.

Explore Product Family →

This guide is an English edition of ASHRAE HVAC Applications Handbook Table 4 adapted to Turkish industry. For many processes ASHRAE values match Turkish regulations and TS EN standards; some sectors (tobacco, hazelnuts, traditional cheeses, hammams and historic buildings) may need local adaptation. We update the guide as standards are revised.

For support in selecting equipment for your sector you can contact us; visit the NKT Akademi homepage for our other guides on psychrometrics and humidity control. As NKT – Nem Kontrol Teknolojileri, we are the authorised Turkish distributor of Neptronic humidifiers; we provide equipment supply, technical support in equipment selection, technical service and spare parts. Engineering design, installation and commissioning are within the scope of the facility's design engineer and installer.