Biosafety cabinets: How to avoid back pain with daily use

Class II biosafety cabinets (BSCs) are valuable laboratory tools that protect the user from hazards and your work from contamination. Most BSCs are set at a fixed height when installed, and the user works in the cabinet by reaching in through the front opening, which is 8 or 10 inches tall and runs the width of the cabinet. The work surface within the cabinet is typically positioned at the height of the lower edge of the front opening or slightly lower. 

BSCs are important laboratory tools for safety and contamination control. While they can be constraining to work in, this is often not a problem as most use is episodic with natural breaks over the course of a day. However, some applications and procedures require more extended work in the BSC, and it is important to reduce the ergonomic stress on these lab technicians. 

Source: Gül and Gül (2018), who looked at workers in two tuberculosis laboratories in Turkey

Biosafety cabinet design and challenges

BSCs are one of the larger pieces of equipment within the laboratory. Most BSCs have mechanically adjustable stands and are typically set so that the work opening is around 30 inches off the floor. It is possible to set the work surface to be higher or lower, although it is less common. You can also change the setting height, but this requires the use of a scissors lift and is not often done.

There are two types of armrests on BSCs. There are some integrated into the lower edge of the opening or even just outside. There are also over-the-grill armrests that tend to be a little farther into the cabinet opening. Armrests on a BSC may feel a little awkward, but they can be beneficial. We need to reach into the BSC to work, so an armrest gives us a “resting reach.” We can extend our hands into the cabinet to work and place our forearms on the armrest, which puts our hands where they need to be. 

A challenge with working in a BSC comes from the fact that people often prefer to move around as they work. Even when seated at a desk, most people shift in their chairs, lean forward and back, in constant adjustment. There is no perfect position, but we move between a variety of positions and postures in a day.

For many users, the BSC is not a problem. Yes, the BSC requires them to sit in a specific place and constrains the movement of their hands and arms to the edges of the front opening, but they only work in the cabinet for limited times during the day. However,  some users need to work at BSCs for longer periods of time, or for an entire shift. Gül and Gül (2018) looked at workers in two tuberculosis laboratories in Turkey and found higher rates of upper extremity diseases due to working with biosafety cabinets. They found 62.5% had shoulder pain, 25.0% had hand wrist pain and 18.75% had elbow pain.

We found that our tall person at 6 feet found it difficult to sit comfortably at a cabinet set with a work surface at 30 inches above the floor

Ergonomic solutions for BSCs

Given the fixed nature of the cabinet, an ergonomic position is achieved by setting the heights of the user’s stool and footrest. 

This can seem like a Rubik’s Cube-like problem. We know what needs to be done and what needs to be adjusted to achieve it, but it seems like we end up trying different things and never really succeed. Also, since many BSC users may not require these adjustments, there is limited discussion on solution strategies. However, there is a method, and it is as easy as 1, 2, 3.

First, place your forearms on the armrest so that they are parallel to the floor and your hands are comfortably positioned in the work area. The angle of your elbows should be 90 to 120 degrees. This is the anchor. The anchor positions our torso a certain height above the floor and a certain distance from the front of the cabinet. We will build our ergonomic position out from here. 

Second, adjust the height of a stool or chair to allow you to sit with your torso comfortably anchored from step one. Your back should be straight. Your anchor placed your torso, and your torso set the stool.