What is Laboratory Ventilation In HVAC and Why Do We Use Them?

Laboratory Ventilation Basics

Laboratories can be dangerous places.

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Because laboratories handle toxic chemicals, combustible substances, flammable solvents, harmful organisms, obnoxious vapours and so on'

Various control measures are necessary to make laboratories safe and comfortable places to work.

Most people are aware that only highly trained and authorised personnel are allowed to work in laboratories, and they use PPE (Personal Protection Equipment such as lab coats, safety goggles, respiratory masks etc). However, some may not know that a lot of effort goes in to incorporating appropriate engineering controls while designing and fitting out new laboratories. This provides safety at three levels ' laboratory users, wider organisation and the surrounding neighbourhood.

For lab designers, understanding of the type of research/activities carried out and regulatory compliance sought by clients is an important step to determine the type and level of ventilation needed for their new facility.

Ventilation is important from a safety as well as financial point of view as it demands major capital and operating costs. Laboratories are energy intensive environments, consuming 4'6 six times more energy per square metre than standard office or commercial buildings and more than 60% of a laboratory's energy consumption can be attributed to the HVAC system (Manufacturing Chemist).

Laboratory ventilation is a complex topic needing specialist input. However, in this article we present an overview and some basics.

HVAC & Lab Ventilation:

A more commonly used term HVAC - Heating, Ventilation, and Air Conditioning - is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and an acceptable indoor air quality. Laboratory ventilation, a part of the HVAC system, is the supply of a fresh/clean air to displace contaminated air and dilute it to safe levels. It consists of two vital factors - air handling and filtration systems.

A basic HVAC unit can be as shown below,

PC: Lightfoot Mechanical

Air is continuously exchanged between buildings and their surroundings. The rate at which air is exchanged is an important property for the purposes of ventilation design and heat loss calculations and is expressed in 'air changes per hour' (ach).

Air changes per hour, or air change rate, abbreviated ACH OR ACPH, is a measure of the air volume added to or removed from a space (normally a room or house) divided by the volume of the space. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced.

Different laboratory areas and rooms in the building will need a different number of air changes. Rooms containing fume cupboards and higher containment need a greater number of air changes than a general laboratory.

The type of material handled in the space will determine if the exhaust needs treating (e.g. HEPA (High Efficiency Particulate Absorption) filters, scrubbers) before discharging into the atmosphere or re-circulating back. For example, biology laboratories, BSL (Biosafety Level) 1 to 4, will involve increasing hazard level and filtration needs. BSL1 being the simplest and BSL4 the most complex.

Pharmaceutical clean room environments need a very high number of air changes as well as HEPA filtration for supply and exhaust air. Check our guidance on clean rooms here.

Guidance on ACH:

In the UK, there are no prescriptive values for air change rates. The rate determined depends on the type of room and the activity being undertaken. Typical industrial applications range between 5 and 15 air changes per hour (CIBSE).

A word of caution about the ACH rate - Ventilation is a tool for controlling exposure. Since a ventilation system designer cannot know all possible laboratory operations, chemicals to be used, and their potential for release of fumes and other toxic agents, single air exchange rate cannot be specified that will meet all conditions.

Furthermore, air changes per hour is not the appropriate concept for designing contaminant control systems. Excessive airflow with no demonstrable safety benefit other than meeting an arbitrary air change rate can waste considerable energy.

An early and accurate assessment of clients' needs, and risk levels through a collaborative approach between lab users, designers, health & safety representatives and M&E engineers/consultants to propose an appropriate ventilation strategy is recommended.

Some or all the criteria below can be used in determining what that looks like:

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• Facility Layout and workflow
• Temperature, relative humidity
• Air pressure differentials between rooms
• Number of air-changes for each room
• Air velocity and airflow pattern
• Number of particles in the air
• Filters (type, position)

Future Trends:

To minimise the energy consumption and environmental impact of ventilation equipment, numerous initiatives have been put in place by the industry to make future labs smarter.  New ways make ventilation central to the design process involving M&E and key stakeholders early in the process, considers it as a dynamic than static process making monitoring and quality control central and the design process focuses on space as activity based zoning and risk assessment for improved efficiency and better control.

Building Choice:

While choosing a new building for laboratory use, it is important to assess the size of the plant room needed and whether enough space is available for distribution of services. Thought needs to be given to structural slab to slab height and to creating sufficient space for a network of supply and exhaust ducts in the chosen building.

Recently, we worked on a project located on an upper floor of a busy city centre building.  Initially, the client had requested high ACH rates throughout the lab (BSL2) area. But constraints with the external and roof top plant space, the lack of ceiling space for extensive ducting and the landlord's reluctance to grant permission allowed us to re-visit their ventilation needs. After individual room analysis and risk assessment a new flexible ventilation strategy was proposed requiring a lesser plant area and improved future energy consumption.

The Goldilocks of Airflow

Too much air and it can feel cold. Too little air and it can feel hot and stuffy. Fluctuations between too much air and too little air speak to a whole different issue! Your TherMOOstat feedback helps us find "just right".

While there aren't clear patterns that too much airflow is always a problem at the air handler, letting us know about airflow abnormalities will help us find malfunctioning mechanical equipment faster. 

Too Much Air, Too Little Air, Is There a Balance?

Airflow is tricky because we must consider how much air is entering a room and how fast it's blowing in. Oftentimes we see TherMOOstat users noticing airflow more than a room's temperature.

Another complexity is all rooms are connected by the air flowing into space. Have you ever opened the door to a room because it was too hot or too cold? While opening the door is one way to manage the temperature, it often affects the surrounding rooms. The stories below are from users that have let us know about airflow issues they noticed, and the mechanical issues we were able to fix. 

Misconception about Ventilation

Stuck in "Perpetual Fan Mode"

We get a lot of comments from TherMOOstat users who feel air blowing all the time, and think something is broken or it's a waste of energy. These users are right that fans do circulate air in occupied buildings, but this is not a mistake.

There are several reasons why the fans keep circulating air when people are in the buildings. The main purpose of 'perpetual fan mode' is to meet ventilation requirements and reduce stuffiness (thereby keeping you comfy)!

1. Ventilation Is Required

We hear your comments. However, ventilation is required. Buildings need to be ventilated when they are occupied (aka 'perpetual fan mode') so they get fresh air and don't feel stuffy. It's actually required by the California Mechanical Code to circulate air through occupied spaces; for our energy nerds out there, see chapter 4 in the Code.

2. People Generate Body Heat

This brings us to our secondary point: body heat. A lot of students in one classroom will generate a lot of heat. The heat produced by all the people in a room means that the space needs circulated air just to compensate for all of the body heat and keep it from getting stuffy.

A Common Ventilation Issue

Poor air distribution or lack of air mixing can be an issue. The cold air coming from the vents may not be mixing well with the warmer air in the rest of the room. This means that cold air is getting dumped on people before it mixes with the rest of the air already in the room. 

One reason for this is the vents aren't adjusted properly. The good news is that we can work together to fix this. Let us know in your comments if you feel pockets of hot and cold air in a room. Darker blue regions on the graphic below represent areas with more airflow and show the uneven distribution. The boxes marked with a letter represent the vents where air enters the space. Read the full story of how we improved comfort.

Ventilation in Different Space Types

Ventilation is the intentional introduction of outside air into a space to improve air quality. Many HVAC systems recirculate some air to save energy, and mix in some outdoor air based on the code requirements for the space type and its designed occupancy (a typical ventilation rate is 15 cubic feet per minute of outdoor air, per person.) In these systems, both the outdoor air and the recirculated indoor air are filtered by the HVAC system before being supplied to the occupied spaces.

Other HVAC systems (primarily those serving lab and animal spaces) operate at 100% ventilation rates, meaning they supply only outside air to occupied spaces and do not recirculate any air.

Laboratory Spaces

The HVAC systems serving laboratory spaces, specifically wet labs, are different from those serving other types of spaces on campus.  The system serving a lab space supplies 100% outside air, meaning no air exhausted from a lab space is recirculated back into the system - it is all exhausted outside the building. Follow the arrows below to see the path that air takes through wet-lab buildings. 

Classroom, Office, and Community Spaces

HVAC systems serving other types of spaces, such as office, classroom, non-wet-labs and/or community spaces have different ventilation requirements than wet-lab buildings. Systems serving non-laboratory spaces are designed to bring in at minimum the amount of outside air required for the design occupancy of the spaces (or the measured occupancy in the case of Demand Controlled Ventilation) and mix it with air returned from the spaces. Most systems are also designed to bring in more outside air (up to 100%) when outdoor conditions are favorable (ie, not too hot or cold). This mixed air is then filtered at the central unit before it is supplied back to the space. Follow the arrows below to see the path that air takes through a non-laboratory building. 

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