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The design and operating characteristics of an environmental chamber which can maintain carbon dioxide concentrations between 1 and 20% and oxygen concentrations between 5 and 21% are described. The chamber, which measures 3.66 x 6.10 m (12 x 20 ft), permits acute and chronic studies to be carried out in either large animals or man. Multiple safety features serve to protect the occupants against failure of equipment or controls. The relative ease with which investigators can work in the chamber, the convenience of long-term operation, and the reliability of the system which controls the gas concentrations provide a unit which has proved useful for the investigation of a variety of physiologic phenomena related to hypercapnia. Preliminary observations indicate that acute and chronic studies of hypoxia will be equally feasible. acid-base; anoxia; respiratory acidosis Submitted on May 11, 1964

Ground silica dust (Mg = 1.3 μ, σg — 1.7) was deposited on Tyler 100 mesh screen at velocities from 3.8 to 27 fps. Particles adhering to the screen were then blown off by filtered air at velocities greater than deposition. Air drag on particles submerged in the laminar boundary layer was calculated from a simple irrotational fluid flow model and compared to particle adhesion force determined in a companion study. Air drag calculated in this manner failed to account for observed particle re-entrainment. Particle re-entrainment, defined in terms of screen pressure loss, was more difficult to achieve as deposition velocity increased. A blowoff velocity of 132 fps, based on screen free cell area, removed essentially all adhering dust from a single screen. During both deposition and dust blowoff procedures, the collector acted as a particle agglomerator and increased particle size by a factor of approximately 2x.

Evaluation of respirators used for protection against dusts, fumes, and mists significantly more toxic than lead can be conducted utilizing a uranine aerosol with a geometric mean size of 0.20 micron. The uranine aerosol is introduced into an exposure helmet chamber which permits exposure of the subject wearing the respirator to concentrations of below 4 mg/m3. The aerosol is collected continuously outside the respirator and during inhalation in the respirator void with membrane filters. Uranine analysis by fluorescence permits evaluation of respirator penetration as low as 0.05% in a fifteen minute study with an exposure concentration of 3 mg/m3.

The Pollak-Nolan nucleus counter was employed to measure efficiencies of various filter media with different size particles at various flow rates. Uranine particles were used, and the filter efficiency determined by the nucleus counter was compared with that obtained by aerosol mass analysis. The two methods are in close agreement for highly efficient media. For media of moderate efficiencies, the efficiency given by the nucleus counter (based on particle number) is much higher in general for the air flows considered, than that given by the aerosol mass determination. The differences in efficiencies may be attributed to the heterogeneity of the size of the particles since the nucleus counter responds more effectively to smaller sizes. A number of comparative tests with several comparable filters were made with atmospheric dust using the Pollak-Nolan counter as for the uranine aerosols. These results agreed with the uranine aerosol measurements.

Measurement of the rate of flow of air during inspiration is important in respiratory physiology and for the design of protective respiratory devices. Methods that have been used previously are described and their limitations explained. A new instrument was constructed for such measurements, which offers no appreciable resistance to air flow. This instrument consists of a microscopic platinum wire suspended across the diameter of a 31.6‐mm tube. One end of the wire is attached to a fixed point and the other end to a fine spring. The displacement of the wire when air flows through the instrument is recorded photographically by a moving paper camera. The deflection of the wire is linear with air flow, and its inertia, lag, and frequency of vibration do not interfere with respiratory measurements. A low resistance valve and mask system complete the apparatus.

This paper describes an improved method for directly measuring low concentrations of carbon monoxide in air. Carbon monoxide reacts with potassium pallado sulfite impregnated on a chemically inert gel contained in sealed glass tubes. Length of discoloration caused by conversion of yellow sulfite to dark brown palladium or its oxide is an exponential function of CO concentration. Data are presented on the measurement of carbon monoxide in air as well as in oxygen-deficient or oxygen-free atmospheres. Applications are given relative to interfering and non-interfering gases and vapors as well as temperature correction data covering range of −50°F to 120°F and ambient pressure correction.

A sampling and handling system for the exhaust of an automotive engine whereby emissions flowing through a through-duct are mixed, extracted through an isokinetic probe, and maintained heated until analysis of the sampled gases is completed. A variable speed pump means is utilized to equalize the instantaneous pressure drop through the probe with the instantaneous pressure drop through the exhaust duct.

This panel discussion created such interest that the introductory remarks of Leslie Silverman, the panel's moderator, and the transcript of the question and answer period which followed the panel's presentation are considered worthy of publication. The two articles by B. E. Saltzman and N. H. Ketcham which immediately follow this article in this issue were a portion of the panel's presentation.

A. simple easily adjustable linear response resistance apparatus is described. The resistance unit contains a glass filter cloth, the effective area of which is adjusted by a mercury column. The resistance of the unit can be adjusted from 0.1 to 1.0 millimeters of water per liter of air flow per minute. The resistance can be easily increased or decreased during the progress of an experiment. The mercury hazard during inspiration was evaluated and not found significant for experiments of one hour.

A self-contained unit for collecting and disposing of chemical fumes, mists, and gases has been developed and field tested. It is portable and compact and, when assembled, only requires connection to an electrical receptacle and water tap to be completely operational. Although originally designed for use in filter type radiochemical laboratory hoods for safe disposal of perchloric acid fumes arising from acid digestions, it may be used as a substitute for a permanent hood in a variety of locations. Collection arid disposal of the acid at the source of emission is the guiding design principle.

THE STUDY of respiratory diseases in children is handicapped by technical difficulties encountered in applying standard methods of measuring pulmonary function, particularly in the youngest age group. Even when nose clip and mouth piece are tolerated, the psychologic reaction to interference with natural breathing is likely to destroy the validity of measurements. The air flow recorder (pneumotachograph) of one of us (L. S.) and associates1appeared to offer a minimum of disadvantages in application to children. Its use is the basis for this investigation. The chief advantage of pneumotachographic recording, apart from its accuracy, is the imperceptible resistance to breathing. The use of a comfortable anesthesia mask instead of a mouth piece and the small size of the apparatus, which can be kept out of sight of the patient, are additional advantages. It has been shown that striking deviations from the normal air flow pattern may be demonstrated with