How far from air intakes should an AGSS exhaust be?

HTM 02-01 (2026) asks for at least 5 m from mechanical inlets and 3 m from passive inlets, at roof level, after a risk assessment.

What is checked at the AGSS exhaust during maintenance?

HTM 02-01 Part B (2026) asks for the exhaust terminals to be examined for occlusion, the exhaust drainage bottles for oil carry-over or condensation, and the warning signage to be confirmed.

Where should an AGSS plant exhaust discharge?

Q: Where should the exhaust of an anaesthetic gas scavenging plant discharge so that gases do not re-enter the building?

Under HTM 02-01 (2026), the NHS England guidance, the AGSS discharge should be sited by risk assessment at roof level, at least 5 m from mechanical inlets and 3 m from passive inlets, not over opening windows or doors, and outside a roof enclosed by a parapet over 100 mm high with air inlets.

Where should the exhaust of an anaesthetic gas scavenging plant discharge so that gases do not re-enter the building?

HTM 02-01 (2026)

For the AGSS discharge outlet, the HTM points to paragraphs 12.48 and 12.49 of its dental scavenging section (12.32): a risk assessment should be undertaken when determining the discharge location of the disposal system, which should be sited at roof level, at least 5 m away from mechanical inlets and 3 m from passive inlets (12.48).
The discharge should not be located over opening windows or doors (12.49).
Where the roof is enclosed by a parapet more than 100 mm high and contains air inlets, exhaust outlets should be located outside the enclosed area, to prevent recirculation of the discharged air (12.49).
The same dental scavenging section also asks for warning signs at the exhaust point (12.50).
The AGS disposal system schematic shows an external exhaust with an insect screen (Figure 24).
For single-chair dental anaesthetic gas scavenging (DAGS), the exhaust should be routed externally in a pipe of at least 32 mm diameter, of a material compliant with fire regulations and sleeved with a copper pipe one size larger (12.47).

The same guidance asks for the air intake of medical air compressors to be located to minimise contamination from internal combustion engine exhausts and from the discharge of vacuum systems, AGSS and ventilation systems (7.23).

Checks in service

HTM 02-01 Part B asks for a monthly check that warning notices are clearly displayed at discharge points, vents, vacuum and AGSS. Its AGSS maintenance tasks include examining the exhaust terminals for occlusion and the exhaust drainage bottles for oil carry-over or condensation, and confirming the terminal warning signage; if condensate is found in the drain flasks, the cause should be investigated and the condensate disposed of as hazardous waste (11.206).

Portugal and the United States

Portugal's ACSS ET 03/2006 (v.2024) asks for the anaesthetic gas extraction exhaust to go to a point outdoors away from air intakes, distant from the medical air compressor systems and from doors, windows and other building openings, with a drain valve and a condensate collection flask (4.9). In the United States, a 2007 NIOSH brochure on waste anesthetic gases asks for the scavenging exhaust to be placed where waste gases will not be reintroduced into the facility's intake air, and the OSHA guidelines (revised 18 May 2000) note that waste gas emissions to the outside atmosphere must meet local, state and Environmental Protection Agency requirements.

The medical vacuum plant has its own exhaust rules; see where a vacuum plant should exhaust.

ULTRASEG

The basic configuration of ULTRASEG, the Ultra Controlo anaesthetic gas scavenging system, includes 1 or 2 condensate collectors.