Workers in cleanrooms and laboratories wear single-use gloves to protect themselves, mainly against chemical and biological risks during handling, but also to protect their work and industrial processes. In some environments or industries, in cleanroom and laboratories, it may be necessary to double-glove, it means wearing two pairs of single-use gloves one on top of the other. This is referred to as double-gloving. These gloves may be made of nitrile or latex and may be sterile or non-sterile. Why double-glove in cleanrooms and laboratories? Whether to protect the worker or to ensure that the manufactured product is not contaminated, it is important to choose the appropriate gloves and follow the double-gloving procedure.

DOUBLE-GLOVING: FOR WHICH ACTIVITIES?

Double-gloving is common in environments where the risk to workers is highest:

 

In laboratories requiring a high level of safety and biosecurity:

• Level 3 and 4 biosecurity laboratories (Laboratories L3 and L4);
• Confined animal units in level 3 and 4 research laboratories.

In these environments, and after carrying out risk assessment, appropriate measures for prevention and the protection of staff, both collective and individual, must be implemented. The nitrile gloves or latex gloves used in these working environments must be:

• Category III PPE (fatal or irreversible risks) in accordance with (EU) Regulation 2016/425 (General requirements for the design and manufacture of Personal Protective Equipment);
• Compliant with ISO 21420:2020 (Protective gloves – General requirements and test methods).

Gloves provide a protective barrier when handling hazardous materials (infectious, toxic) or equipment potentially contaminated with these materials, infected animals, etc. Gloves can also deteriorate during handling by the operator and may no longer provide sufficient protection. Therefore, doubling laboratory gloves reduces the deterioration of the inner glove (the one in contact with the skin) and ensures better protection for the operator.

In hospital pharmacies where cytotoxic products are handled, notably during cancer treatments:

The use of (sterile or non-sterile) single-use gloves constitutes the first line of protection for operators handling chemotherapy products. Since the gloves are therefore intended to protect the wearer, they must be registered in accordance with (EU) Regulation 2016/425 on Personal Protective Equipment (PPE). This regulation concerning PPE differs from that concerning medical devices ((EU) Regulation 2017/745).

Since some cytotoxic products have a high penetration power and, in general, these products have a toxic effect on human cells, double-gloving with sterile gloves is particularly recommended during the production and preparation phases, in order to obtain a total thickness of at least 0.2 mm to 0.3 mm (according to the local reference standard). This is because it is unlikely that any micro-holes will be present on both pairs of gloves and in the same places. In general, sterile gloves should be changed regularly (approximately every 30 minutes to one hour or every 4/5 operations) to avoid skin contact.

Double-gloving is also common in the manufacturing of products that must be kept free of contamination:

 

This is the case for operations in aseptic environments and in controlled atmosphere areas (cleanrooms) in the pharmaceutical industry:

Sterile medicinal products are manufactured in a Controlled Atmosphere Zone (CAZ) in compliance with good manufacturing practices (GMPs). In these areas, the risk of particulate and microbial contamination of products must be minimized. The first reason for wearing gloves in these areas or, more generally, in cleanrooms, is therefore to avoid product contamination. This is because any detected contamination would lead to both the loss of the manufacturing batch and therefore financial losses. If contamination were not detected, the risks to the consumer would be significant and the consequences for the manufacturer potentially severe.

Sources of contamination:

• Human (skin cells, hair, microorganisms, bacteria, or viruses);
• Particles present on PPE (including gloves).

It is therefore essential to maintain the cleanliness of cleanroom environments by wearing gloves of a high level of cleanliness with a low particle content and which are long enough to cover the wrist of the suit.

Double-gloving ensures that the aseptic environment (Class A or B) is maintained by adhering to clothing procedures that require the wearing of ultra-clean sterile gloves before putting on a complete set of sterile garments, including a second pair of sterile cleanroom gloves.

Furthermore, in life sciences and in many environments, it is very common to have to carry out regular disinfection of outer gloves (those not in contact with the skin) using products such as 70% Isopropanol. This successive spraying or wiping with pre-saturated wipes (approximately every two minutes or after each critical action) causes the gloves to deteriorate. It is therefore necessary to change outer gloves regularly. Wearing two pairs of sterile gloves means that only the outer glove has to be changed without leaving the workspace. Any exit involves a complete, time-consuming, and therefore costly undressing and dressing procedure.

CHOOSING THE RIGHT GLOVES FOR DOUBLE-GLOVING

 

• Suitable glove length: the protection of workers and the product requires the use of gloves that protect against various risks (chemical, biological, viral, etc.) but that are also adapted in terms of length. For better protection, it is preferable that the cuff of the outer glove be long and well-adjusted so as to fit over the sleeve of the laboratory coat or cleanroom suit to hold it in place and avoid any exposure of the wrist or arm, and to facilitate the disinfection of the forearm. At SHIELD Scientific, we recommend wearing an outer glove that is as long as or longer than the inner glove. This is because with a longer outer glove, glove changes are easier thanks to an easier grip on the outer glove without the risk of touching the inner glove.

 

• Detection of micro-holes: Harmful substances and particulate and biological contaminants can pass through possible micro-holes in gloves. It is therefore necessary to:
  • Select gloves with the lowest possible AQL (tested in accordance with ISO 374-2:2019), which therefore provide a better barrier performance. There are disposable gloves with an AQL of 0.65 or even lower (0.25).
  • Note that wearing a coloured inner glove with a white or natural-coloured outer glove makes it easier for the operator to detect defects, such as possible micro-holes.

 

• Protection against chemical and biological hazards: There is no single-use glove that can protect in all situations. The nature of the risk, the task to be performed, the worker and the working environment must therefore all be considered. This means ensuring that:
  • • The selected gloves meet the performance requirements for chemicals as defined in ISO 374-1:2016+A1:2018 and the performance requirements for microorganisms in accordance with ISO 374-5:2016;
    • With regard to the handling of cytotoxic products, it is also important to ensure that the gloves have been tested according to the ASTM D6978-05 (2019) standard, which has been specially developed for operators exposed to this type of agent and which is much more sensitive than the European test EN 16523-1:2015+A1:2018.

 

• Ultra-cleanliness of the glove: To maintain the highest level of cleanliness in a controlled atmosphere environment, gloves must be washed one or several times in deionized water to meet the required particle level specifications. The more the glove is washed, the better the contamination control.

 

• Sterile or non-sterile gloves: the use of sterile or non-sterile gloves depends on the task to be performed and the working environment.

 

SHIELD Scientific offers several glove combinations for use in a double-gloving procedure:

The most common combinations of double-gloving sterile gloves for activities in aseptic production areas:

The most common combinations of double-gloving non-sterile gloves for biosecurity laboratory activities:

In conclusion, Health & Safety, Production, Quality and Sterility Managers and users of disposable gloves need to consider a number of factors when choosing the right protective laboratory or cleanroom gloves to meet the objectives set. Double-gloving ensures the safety of workers, products and the environment while maintaining comfort and dexterity. Gloves that are easy to put on and take off are an additional factor in productivity and safety.

Stay tuned: soon, our sterile gloves double-donning procedure in grade A/B cleanroom in the pharmaceutical industry.