Safety in Design

7 The Risks of Enclosed Spaces

7.1 Introduction

The reduction of oxygen (O₂) concentration in air by inert gases is a risk of enclosed spaces. A further risk is intoxication by absorption of hazardous toxic materials through the lungs. Inhalation of dust and particulate matter can also be a serious respiratory problem. The focus in this chapter is on the first two risks. Toxic materials can be classified in terms of their physiological action:

• Irritants, which includes corrosive gases/vapors that attack the mucous membrane surfaces of the body. Sulfur dioxide and chlorine are examples.
• Asphyxiants, which are substances that interfere with the oxidation processes in the body. The simple asphyxiants are physiologically inert gases, which dilute or replace the oxygen required for breathing. Dilution of air by the simple asphyxiant nitrogen (N₂) was probably the cause of the accident described in Section 7.3, the section concerning industry. Consumption of oxygen in air by fire was probably the cause of many casualties at a fire described in Section 7.4.1, part of the section on society. Chemical asphyxiants react with an essential body function involved with the transportation of oxygen (O₂) from the lungs via red blood cells to body tissues. In such cases, asphyxiation results even though the air contains an adequate concentration of O₂. Chemical asphyxiation by carbon monoxide (CO) was the cause of the accident described in Section 7.2, the section regarding transport. ...