Why Low Humidity Is Critical for Cleanroom Contamination Control | Cleanroom HVAC Design Dublin, Ireland
- MTS DNC ENERGY CONSULTANTS LIMITED
- 2 days ago
- 5 min read
When discussing contamination control in pharmaceutical manufacturing, biotechnology facilities, hospitals, and medical device production, much of the attention focuses on HEPA filtration, pressure cascades, and personnel gowning. However, one environmental parameter plays an equally important role in reducing microbial contamination—relative humidity (RH).
Micro-organisms require moisture to survive and multiply. By carefully controlling humidity, cleanroom designers create an environment that is significantly less favourable for bacterial and fungal growth while also protecting moisture-sensitive products.
At MTS DNC Energy Consultants, we specialise in M&E Design in Dublin, Ireland, delivering advanced HVAC design, cleanroom HVAC design, contamination control strategies, and GMP-compliant pharmaceutical engineering solutions.
What Are Micro-Organisms?
Micro-organisms are microscopic living organisms found virtually everywhere on Earth. Although invisible to the naked eye, they play a significant role in both human health and pharmaceutical manufacturing.
The most common groups include:
Bacteria
Viruses
Yeasts
Moulds (Fungi)
Parasites
While many microorganisms are harmless—or even beneficial—others can contaminate pharmaceutical products, medical devices and sterile manufacturing processes.
Earth Is Covered with Microbial Life
The scale of microbial life is almost impossible to imagine.
Scientists estimate that Earth contains approximately:
50 Nonillion Micro-organisms
That's:
50,000,000,000,000,000,000,000,000,000,000
By comparison, the world's human population is approximately:
8 billion people
Micro-organisms exist:
In the air
In water
In soil
On plants
On animals
On every human being
This enormous microbial population explains why contamination control is one of the most important aspects of cleanroom HVAC design.
What Do Micro-Organisms Need to Grow?
Just like humans, microorganisms require favourable environmental conditions.
The five essential requirements are:
1. Oxygen
Many bacteria require oxygen to survive (aerobic bacteria), although some thrive without oxygen (anaerobic bacteria).
2. Water (Moisture)
Water is the single most important requirement for microbial growth.
Without sufficient moisture:
Bacteria cannot reproduce effectively.
Fungal growth slows dramatically.
Many microorganisms become dormant.
Water availability is therefore one of the primary factors controlled within pharmaceutical cleanrooms.
3. Temperature
Microorganisms grow fastest within specific temperature ranges.
Many bacteria associated with humans grow best between:
20°C and 40°C
This overlaps with normal room temperatures, making temperature control another important engineering consideration.
4. pH
Different microorganisms require different acidity or alkalinity levels.
Most bacteria prefer conditions close to neutral:
pH 6.5–7.5
5. Nutrients
Microorganisms require nutrients such as:
Proteins
Sugars
Organic matter
Even tiny particles of skin, dust or residues can provide enough nutrients for microbial growth.
Why Moisture Is So Important
Moisture provides the ideal environment for bacterial growth.
Examples include:
Bathrooms
Kitchens
Standing water
Condensation
Wet processing equipment
Within the human body, bacteria thrive in naturally moist areas including:
Mouth
Nose
Eyes
Respiratory tract
This is one reason why people remain the largest source of viable contamination in cleanrooms.
The Importance of Relative Humidity in Cleanrooms
One of the most effective engineering controls available is relative humidity (RH).
Many pharmaceutical cleanrooms operate at:
≤30% Relative Humidity
particularly where moisture-sensitive products are manufactured.
Maintaining low humidity reduces the amount of available moisture required by microorganisms to grow.
Benefits of Low Humidity in Cleanrooms
Maintaining humidity below approximately 30% RH provides several advantages.
Reduced Bacterial Growth
Bacteria require moisture to multiply.
Lower humidity makes survival and reproduction more difficult.
Reduced Mould and Fungal Growth
Fungal spores require moisture before they can germinate.
Lower humidity greatly reduces this risk.
Less Surface Condensation
Condensation creates ideal environments for microorganisms.
Controlling humidity helps keep surfaces dry.
Improved Product Stability
Many pharmaceutical ingredients are hygroscopic and absorb moisture.
Low humidity protects:
Powders
Tablets
Capsules
APIs
Medical devices
Improved Cleanroom Performance
Low humidity complements:
HEPA filtration
Pressure cascades
Air change rates
Temperature control
Environmental monitoring
Together these engineering controls minimise contamination risks.
Does Low Humidity Make a Cleanroom Sterile?
No.
This is an important distinction.
A low-humidity environment is not sterile.
Sterility means the complete absence of viable microorganisms and can only be achieved through validated sterilisation processes.
Low humidity simply creates an environment where microorganisms are much less likely to survive and multiply.
A truly sterile pharmaceutical cleanroom relies on multiple layers of protection including:
HEPA filtration
Controlled airflow
Pressure differentials
Temperature control
Relative humidity control
Cleaning and disinfection
Environmental monitoring
Personnel gowning
GMP procedures
This layered approach is known as Contamination Control Strategy (CCS) under EU GMP Annex 1.
The Role of HVAC Design in Humidity Control
Maintaining humidity below 30% RH requires specialist HVAC design.
A pharmaceutical HVAC system typically includes:
Air Handling Units (AHUs)
Cooling coils
Heating coils
Desiccant dehumidification (where required)
HEPA filters
Humidity sensors
Building Management Systems (BMS)
The HVAC system continuously conditions incoming air to maintain stable temperature and humidity throughout the cleanroom.
Poor humidity control can result in:
Increased microbial growth
Condensation
Product degradation
Static electricity
Regulatory non-compliance
Why M&E Design Matters
Effective contamination control requires far more than selecting an AHU.
Professional M&E Design in Dublin, Ireland integrates:
HVAC systems
Mechanical ventilation
Heating and cooling
Cleanroom pressurisation
Electrical systems
Building Management Systems
Energy efficiency
Sustainability
Regulatory compliance
A properly coordinated mechanical and electrical design ensures that every building system works together to protect products, patients and manufacturing processes.
Key Takeaways
Microorganisms require oxygen, water, temperature, nutrients and the correct pH to survive.
Moisture is one of the most important factors influencing microbial growth.
Maintaining relative humidity below 30% RH helps reduce bacterial and fungal growth.
Low humidity does not sterilise a cleanroom but forms an important part of a comprehensive contamination control strategy.
Effective cleanroom HVAC design combines humidity control with HEPA filtration, airflow management and pressure cascades.
Professional M&E Design in Dublin, Ireland ensures pharmaceutical facilities remain energy-efficient, GMP-compliant and capable of maintaining strict environmental conditions.
Final Thoughts
Humidity control is often overlooked, yet it plays a fundamental role in pharmaceutical contamination control. By limiting the moisture available to microorganisms, cleanroom HVAC systems help create conditions that discourage microbial growth, protect sensitive products and support compliance with EU GMP Annex 1 and ISO 14644.
However, humidity control should never be viewed as a standalone solution. The most effective cleanrooms combine low humidity with high-efficiency filtration, controlled airflow, rigorous cleaning procedures and disciplined operator behaviour to create a robust contamination control strategy.
At MTS DNC Energy Consultants, we provide specialist M&E Design in Dublin, Ireland, including HVAC design, cleanroom HVAC design, pharmaceutical building services engineering, energy modelling and GMP-compliant environmental control solutions for life science, healthcare and advanced manufacturing facilities.
How Our Consultants Can Help
At MTS DNC Energy Consultants, we provide:
Heat pump assessments
Part L compliance reports
Building energy modelling
Through NEXUS M&E Design, we also deliver:
Heat loss calculations
Heat pump sizing
Radiator and underfloor heating design
Mechanical ventilation design
We ensure every system is designed for maximum efficiency, compliance, and long-term performance.
Disclaimer
The content shared in these posts is intended for informational purposes only and should not be interpreted as design advice, specifications, or a calculation template. For professional guidance or design services, please contact us through our contact form.