Section 2 Analysis of Common Problems in Medical Laboratory Design and Construction

I. Issues to Note in Cleanroom Engineering

1. Problems That Easily Occur in Cleanroom Engineering

(1) Bacteria and airborne dust trapped by the filter membrane cannot be killed, and under suitable temperature and humidity they readily multiply on their own, causing contamination, mold growth, and similar phenomena; continued use very easily leads to secondary contamination.

(2) Because atmospheric pollution is severe, the filter membrane is very easily blocked and must be replaced frequently, resulting in high and cumbersome operating costs.

(3) Although relying on high-efficiency filter membranes solves the cleanliness problem, the odors of toxic and harmful gases inside the cleanroom as well as the chemical contamination generated by the purification system itself cannot be resolved.

2. Solutions

An electrostatic sterilization and purification cabinet is used to kill bacteria, disinfect, and remove airborne dust. The electric field in the electrostatic sterilization and purification cabinet uses a dual-zone electrostatic field of round-hole needle type and honeycomb rod type; the dual zones refer to the polarization zone and the dust collection zone. When the air delivered from the ventilation duct passes through the dual-zone electrostatic field, contaminants such as bacteria and airborne dust in the air are first polarized by the electrostatic field. Because the bacterial cyst itself carries a negative charge, it is recharged with high-energy negative charges when passing through the electrostatic polarization zone. When negatively charged contaminants such as bacteria and viruses enter the dust collection zone of the positive electric field through the system, they are immediately and strongly attracted and collected by the positive dust collection plates of the dust collection zone. Under the action of the positive electrode, the cysts are instantly shattered and killed, thereby achieving the purpose of sterilization and disinfection. At the same time, the electrostatic field exerts a strong attraction, collection, and agglomeration effect on airborne dust in the air, which effectively protects the high-efficiency filter membrane and extends its service life. It can be conveniently removed, and after the purification cabinet is cleaned it can be used repeatedly, reducing the operating cost of the system.

Titanium-carbon mesh and photocatalyst technology are applied to remove harmful gases and odors. A photocatalyst is a nanoscale titanium dioxide active material; it is coated onto the surface of a substrate and forms a thin film after drying. Under the action of light, it produces a strong catalytic degradation function: it can effectively degrade toxic and harmful gases in the air, effectively kill many kinds of bacteria with an antibacterial rate as high as 99.99%, and decompose and render harmless the toxins released by bacteria or fungi; at the same time it also has functions such as deodorization and anti-fouling.

II. Issues to Note in the Design and Construction of Cleanroom Engineering

In recent years China has built some BSL-3 biosafety laboratories, some of which are successful, but there are indeed some with certain defects, mainly because their builders are not very clear about the key technical points of biosafety laboratories. Therefore, although they used many high-grade and expensive building materials, the laboratories still fail to meet requirements. The design drawings provided by some companies are in essence ordinary negative-pressure laboratories and simply cannot meet the requirements of biosafety laboratories.

1. Air-Conditioning and Ventilation System

The airflow organization inside a biosafety laboratory must be rational, avoiding too many dead corners. Biosafety laboratories require that airflow must flow from the clean zone to the contaminated zone. The positions of indoor air supply and exhaust outlets should minimize the space where airflow stagnates, and the indoor exhaust outlets should be set in the most hazardous area, arranged on one side without obstruction.

The installation positions of filters in the exhaust system should be rational and convenient for leak testing and replacement. High-efficiency filters should not be installed at the positive-pressure end of the exhaust fan, because this neither protects the fan nor meets the requirement that the contaminated exhaust section must be under negative pressure.

Split air conditioners or floor-standing air conditioners should not be installed indoors, because the heat exchanger in an air conditioner is in fact a microbial breeding device that would seriously contaminate the laboratory environment.

Some construction units, rather than installing split or floor-standing air conditioners inside the laboratory, install them in adjacent rooms and use ducts to supply air. However, because high-level biosafety laboratories must use once-through airflow fans, while the heat exchanger of an ordinary air conditioner is designed for indoor recirculated air and cannot achieve the large enthalpy difference required for once-through airflow—and in addition, in order to reduce cost, the equipment capacity has no margin—the required indoor temperature simply cannot be reached. Conducting experiments in a high-level biosafety laboratory requires wearing special protective clothing, sometimes multiple layers; if the temperature does not meet requirements, the experimenters will feel uncomfortable.

The exhaust system must be fitted with high-efficiency filters and cannot rely solely on high-altitude discharge. Some design or construction units have a deficient understanding of high-speed discharge, believing that high-speed discharge means the air velocity in the exhaust duct must exceed 13 m/s. As a result, the exhaust resistance is large and the required exhaust volume cannot be reached, making it very difficult to maintain the required negative pressure indoors; or the exhaust fan pressure is too large, simultaneously increasing noise and power consumption.

2. Equipment Backup Issues

BSL-3 and BSL-4 biosafety laboratories must be provided with backup power. For example, BSL-3 biosafety laboratories require two independent power supply routes or a backup generator set, while BSL-4 biosafety laboratories require a third backup power source. Where conditions are not available, an uninterruptible power supply (UPS) must be additionally provided, whose power supply capacity is required to be no less than 45 min.

BSL-3 and BSL-4 biosafety laboratories must be provided with exhaust fans; this is to ensure that negative pressure is maintained inside the laboratory under all circumstances. When an exhaust fan fails, the backup exhaust fan should be able to automatically come into operation.

3. System Regulation and Control Functions

To strictly ensure the pressure differences and pressure gradients among the various functional areas within the laboratory, necessary air volume regulating devices and constant-air-volume valves should be installed on the air supply and exhaust systems, rather than using ordinary regulating valves as substitutes.

4. Attach Importance to Engineering Testing

After a biosafety laboratory is completed, it must first be tested by a nationally authorized testing institution; this is a very important step. The testing content should include many aspects such as the airtightness of the laboratory, the negative pressure values between rooms, air flow direction, high-efficiency filter leak testing, cleanliness classification, and the automatic control system.

5. Other Points of Attention

It is strictly forbidden to build a biosafety laboratory as a positive-pressure laboratory; fire dampers must be installed as specified; it is strictly forbidden to substitute a clean bench for a biosafety cabinet; and it is strictly forbidden to substitute the exhaust of a safety cabinet for room exhaust. An ordinary clean bench and a biosafety cabinet have completely different working principles and uses and simply cannot protect the human body from microbial infection, which is extremely dangerous.

III. "Three Wastes" Treatment Issues

The daily work of laboratories frequently generates and discharges some toxic and harmful gaseous, liquid, or solid substances. Without certain protective measures and treatment methods, these will cause adverse consequences for humans and the environment. Laboratory "three wastes" are characterized by small quantities, miscellaneous types, and relative dispersion, and are not easy to treat. Many laboratories do not treat the "three wastes" well, and some do not treat them at all.

  1. Laboratory wastewater: the composition of laboratory wastewater is complex and variable. A simple and feasible treatment method is to build a wastewater tank in which acidic and alkaline wastewater are neutralized; the pH of the wastewater is adjusted to slightly alkaline, a flocculant is added for sedimentation, and the supernatant wastewater can be directly discharged or sent into the sewage pipe network. The sediment is treated and then disposed of as solid waste.

  2. Laboratory waste gas: laboratory waste gas is mainly of two major categories: acid mist and organic gases. Operations generating the two types of contamination should preferably be carried out in different fume hoods. Acid mist gases are treated with an alkaline aqueous solution absorption tower; the spray pump of the absorption tower is interlocked with the fume hood switch, and the aqueous solution in the absorption tower is fitted with pH monitoring equipment. Organic waste gas can be treated with high-efficiency adsorption devices.

IV. Deficiencies Existing in Construction and Renovation

  1. The laboratory area planning is not sufficiently rational. For example: routine analysis and instrumental analysis share the same room, the sample storage and reagent storage share the same room or are not strictly separated, and office areas and experimental areas overlap.

  2. The selection of air-conditioning equipment is irrational or the installation is inadequate; in some cases it even causes water dripping above the laboratory instrument benches.

  3. The air outlet equipment of the air-conditioning system is irrational, with air outlets facing instruments and equipment, affecting their normal operation.

  4. The exhaust and fume removal systems are poorly designed and ineffective.

  5. The power supply lines do not separate strong current, weak current, and instrument power.

  6. The grounding wires of precision instruments do not meet requirements.

  7. Humanistic care is insufficient. No storage places are provided for staff members' personal belongings, such as lunch-break beds and rice bowls.

  8. The overall design lacks forward-looking awareness, failing to take network, telephone, surveillance, fire protection, and access control into account together.

  9. Investment in environmental protection facilities is insufficient; in some cases they are not even included in the design.

  10. Because the design is not sufficiently thorough, too many items are added or replaced during construction, causing the budget to be exceeded by too much.

V. Electrical Safety

Electric shock accidents and fire accidents occur from time to time in laboratories, and the losses from each accident are always extremely heavy and the harm enormous. How to avoid the occurrence of electric shock accidents and fire accidents is the foremost issue that should be considered during laboratory construction.

  1. The installation and use management of electrical equipment inside the laboratory must comply with the safety electricity use management regulations. High-power laboratory equipment must use dedicated power lines, and sharing with lighting lines is strictly prohibited, to guard against fires caused by overload electricity use.

  2. One must have a clear picture of the locations and devices inside the laboratory that may generate static electricity; they must carry clear markings and warnings, and proper preventive measures must be taken against the hazards they may cause.

  3. A three-phase five-wire system is used to prevent instruments from becoming live and to prevent electric shock accidents. According to the relevant building standards, this means three phase wires, one ground wire, and one neutral wire. Even when the three-phase load is extremely unbalanced, causing the neutral wire to become live, the voltage of the independently grounded ground wire always remains zero, which can prevent instruments from becoming live and prevent the occurrence of electric shock accidents.

  4. To eliminate fires, strengthening the sense of responsibility of laboratory personnel is necessary, but ensuring that there is no electricity in the laboratory when it is unoccupied is even more reliable. Each laboratory (including the supporting preparation rooms and offices) has one master switch, ensuring that experimenters cut off the laboratory's main power nearby when leaving the laboratory; refrigerators, incubators, and the like that cannot be powered off are provided with separate circuit switches. This effectively prevents fires caused by negligence.

VI. Water Use Safety and Control

Water flooding and other accidents caused by water leaks in laboratories occur from time to time, and their hazards and losses are often also very serious. The causes are mainly damage to some component in the water supply system or forgetting to turn off a faucet after an occasional water cutoff, especially at night or during holidays when the laboratory is unoccupied.

The experience of many laboratories shows that an effective control method for the water supply safety of each laboratory is to have one master gate valve controlling the water supply of the entire laboratory. Every day before leaving work, the last person to leave the laboratory closes the master gate valve, which can ensure that no water leak accident occurs in the laboratory. To allow for handling a failure of the master gate valve, an inspection gate valve is added before the master gate valve. During the construction design process, regardless of whether a horizontal main pipe or vertical main pipe system is adopted, each laboratory may have only one main water pipe introduced, with two master gate valves pre-connected in series, which is conducive to the control and safety of laboratory water use.

VII. Other Problems

  1. After the laboratory is completed, it cannot meet the client's actual needs. For example: after the laboratory is completed, many problems are found to have been overlooked in the design, including inability to install instruments, absence of a water source or power source, or interfaces not located nearby; the floor is easily scuffed; the workflow is not smooth; ventilation is insufficient; space is inadequate; there is no vibration isolation equipment; temperature and humidity recording and control cannot operate normally; and decorative materials do not meet requirements.

  2. The final settlement of the laboratory far exceeds the budget. This is currently the most common problem in laboratory fitting-out. For example, a project awarded at 4.8 million yuan may require 6 million yuan at settlement.

  3. The maintenance and repair of the laboratory cannot be carried out normally. When the completed laboratory enters trial operation, many problems may be discovered but cannot be corrected in time; construction units often claim that this is a design problem, and responsibilities are unclear. Therefore, one should not adopt a free design scheme; a company with relevant design experience must be engaged for professional design, a design contract should be signed, and a reasonable design fee paid, to avoid greater losses from irrational engineering construction later caused by coveting free design.

  4. The laboratory cannot meet the needs of further development. After construction according to the design drawings, the resulting laboratory cannot be further developed—for example, there is no space for new instruments and equipment, and computer interfaces are not installed, so the equipment cannot meet the requirements of information-based construction.

  5. The laboratory does not meet fire protection requirements. Some laboratories are built without undergoing fire protection review.

  6. The laboratory has occupational hazard risks.